How geofencing proves you were there, without killing your battery

Here's the uncomfortable truth about most habit and consistency apps: they don't actually know whether you did the thing. You tap "complete," and they believe you. That's fine when the only person you're accountable to is yourself and the only thing at stake is a streak. It falls apart the moment real money is on the line.

If Commity is going to charge you for missing a day, the bar is higher: it has to know you were there, and it has to be something you can't fake to yourself at 11pm. So a tap in Commity isn't a checkbox — it's a GPS-verified check-in. You tap "I'm here" when you arrive, and your phone's location has to back you up before a single minute counts.

What a geofence actually is

A geofence is just a virtual circle on the map: a center point and a radius. When you create a commitment, you pin the place where you want to show up — your gym, your studio, the library — and that becomes the center. The fence is what decides whether your "I'm here" actually counts: tap it inside the circle and you're in; tap it from across town and Commity politely tells you you're not there yet.

Once you're checked in, Commity logs the minutes you actually spend inside the fence. Hit your daily goal — say 60 minutes — and the day is marked complete and your stake is safe. The tap is the one thing you do; everything after it is automatic. You show up, you tap, and being there is the proof.

The battery problem (and how we dodge it)

The naive way to build this would be to ask the phone for a high-accuracy GPS fix every few seconds, all day. That works for exactly one afternoon, until your battery dies and you uninstall the app. Continuous high-accuracy GPS is one of the most battery-killing things a phone can do.

So Commity never does that. It does two things instead: it only ever watches the spot you pinned — never everywhere you go — and it scales how hard it looks based on how close you actually are:

• Far from your spot: cheap, low-power checks. When you're nowhere near your place, Commity takes only occasional, low-accuracy readings — just enough to notice when you're getting close. No constant high-accuracy GPS.
• Near your spot: precise GPS kicks in. Once you're close to your fence, Commity switches on accurate tracking so it can catch the exact moment you arrive and leave, and count the minutes inside.
• Goal hit, or a rest day: nothing at all. The moment you complete the day's goal — and on any day you didn't schedule — tracking idles completely. There's nothing to watch, so it doesn't.

This is also why Commity asks for background ("Always") location: that's what lets it notice you've arrived and keep your timer running even when the app is closed or your phone is locked. The trade is deliberate — it's allowed to watch your one spot in the background precisely so it doesn't have to run at full power all day. Most of the time it's doing the lightest possible work, and the expensive, precise part only runs in the short window when it actually matters.

Does it keep counting when the app is closed?

Yes. The one thing that needs the app open is the tap — you open Commity and tap "I'm here" when you arrive. From that moment your timer keeps running on its own, no matter what you do with your phone:

So the model flips the hard part on its head. Instead of relying on your phone to magically notice you arrived — which, on iPhones especially, can be slow or unreliable — Commity asks for one deliberate tap, and in exchange the rest is rock-solid: starting, counting and finishing all just work. And so you never forget that tap, Commity nudges you when you're near your spot, and again in the evening if you haven't checked in. The nudge is a helpful reminder, not the thing keeping score — the tap is always there as the sure way in.

The honesty problem: GPS wobble

Here's the subtle part most people never think about. GPS isn't a clean signal. Even when you're standing perfectly still, the reported position drifts several meters around — bouncing off buildings or fading indoors. If you treated every reading literally, a single noisy fix near the edge of your fence would register as "left the gym," then "came back," then "left" again — shredding one honest 60-minute workout into dozens of meaningless fragments.

The goal isn't to react to every GPS reading. It's to figure out the truth despite them.

Your check-in is settled the instant you tap — a clean, verified reading, no wobble involved. The wobble only matters afterwards, for deciding when you've left. So Commity guards the exit with a few "anti-flap" tricks:

• Hysteresis. You're counted as present the moment you tap in, but you're only counted as gone once you're clearly past the fence — not the instant a reading nudges over the line.
• An accuracy gate. A low-confidence fix (the phone tells you how accurate each reading is) is never trusted to end a visit. A fuzzy reading can't kick you out.
• Debounce. Leaving requires several consecutive confident "outside" readings, not one. A momentary glitch can't end a session you're still in the middle of.

Together these mean a single bad reading never costs you a session — but a genuine departure is still caught quickly. This means that the departure might take a little longer, which protect the person who actually showed up.

Done the instant you hit your goal

You don't have to leave for the day to count. The moment your time inside crosses your target — the 60th minute of a 60-minute goal — the day flips to complete right there on the spot: your stake is locked safe, you get a "Goal hit!" buzz, and the evening's "you haven't shown up yet" reminders are cancelled so the app stops nagging you. Tracking for that place then goes quiet for the rest of the day. Spending an extra hour at the gym doesn't change anything, and walking out later can't accidentally double-count the visit — once it's earned, it's settled.

Day-scoped, so midnight is clean

One more detail that matters when money's involved: each session belongs to a single day. Your minutes are banked against today's goal, and the clock doesn't quietly drag a late-night visit across midnight into tomorrow. When the day rolls over, today's tally is settled on its own terms. It keeps the accounting honest and predictable — which is the least you should expect from something that can charge you.

Why it's built this way

Every one of these decisions comes back to a single principle: the proof has to be real, and it has to favor the honest user. A naive check-in button fails both tests — it's fakeable, and it tempts you to cheat yourself. Commity's check-in is different: the tap only counts if your GPS proves you're standing at your spot. You get the honesty of a geofence with the reliability of one deliberate action — you can't tap your way to a completed day from the couch, and a flaky GPS reading can't rob you of one you earned.

That's the quiet engineering behind a simple promise: show up, tap once, and Commity will know.