What Is a Geofence Reminder? Location Alerts Explained
A geofence reminder rings when you arrive somewhere, not at a time. How it works on Android, the right distance, battery, privacy, and why one may not ring.
You walk into the bank and your phone says: “You’re at the bank. Deposit the day’s cash.” Nobody set a time. The phone simply knew you had arrived. That is a geofence reminder.
This article explains what a geofence is, how a phone knows you have arrived, how to choose a good distance, what it means for your battery and your privacy, and why a reminder sometimes does not ring. The examples use Karo’s place reminders, a free feature of the Karo app on Android.
What is a geofence?
A geofence is an invisible circle drawn around a place on the map: a point (your shop, your home) and a distance around it (say 100 metres). Your phone can watch that circle and tell an app when you enter it or leave it.
A geofence reminder, also called a location-based reminder or a geo notification, is a reminder tied to that circle instead of to a clock. It rings when you arrive, which is exactly when you can do the task.
Time reminders vs place reminders
| A time reminder | A place reminder | |
|---|---|---|
| Rings | At 6 pm | When you reach the warehouse |
| Good for | Calls, deadlines, meetings | Tasks that can only be done somewhere |
| The problem it solves | Forgetting a deadline | Being in the right place and forgetting |
| Example | “Call the CA at 11” | “Count the cement bags” at the warehouse |
Many tasks need one or the other. Some need both: a due date so it gets done this week, and a place so you remember it the moment you are there. In Karo, a task for yourself can have both.
How the phone knows you have arrived
On Android, Karo hands your places to the phone’s own geofencing, part of Google Play services. Android watches the circles quietly, mostly using Wi-Fi and mobile networks, and wakes Karo only when you cross into one. Karo does not keep GPS running all day.
That is why Android asks for a few things before place reminders can work:
- Location on, and Google’s location accuracy on: geofencing relies on it.
- Precise location for Karo: approximate location cannot tell one street from the next.
- Allow all the time: the reminder has to ring while Karo is closed, which is most of the time.
- Notifications on: otherwise the reminder has nowhere to show.
Karo shows which of these is missing, with a button to turn it on.
Choosing the right distance
The distance (the circle’s radius) is the most important setting. Too small and the reminder can miss you; too large and it rings while you are still down the road.
- Indoors, a phone’s position can be 20–50 metres out. So in Karo the smallest circle is 50 metres, and a new place starts at 100 metres.
- 100 m suits a home, a small shop or a clinic.
- 150–200 m suits an office in a tall building or a crowded market, where the location wobbles more.
- 500 m to 1 km suits a factory, a warehouse yard or a large campus.
A good test: if a reminder rings late or not at all, make the circle bigger. If it rings too early, make it smaller.
Not ringing again and again
At the edge of a circle, a phone’s position can jump in and out several times while you sit still. A good geofence reminder should not ring each time. In Karo:
- It rings once per visit. Stepping out for less than 15 minutes and coming back is the same visit.
- It never rings twice for the same place within two hours.
- If you saved the place while standing there, that is not an arrival. The next time you arrive, it rings.
Battery
Karo watches only the places that have open tasks (or a repeating task) for you. When none are left, it stops checking altogether. And because Android’s geofencing does the watching with network location rather than constant GPS, it is light on the battery.
Some phone makers add their own battery savers that stop apps which are swiped away. If reminders do not arrive on such a phone, let Karo run in the background in the phone’s battery settings.
Privacy: where your location goes
A geofence reminder needs your location, so it is fair to ask where that location goes. In Karo:
- Your phone works out where it is on the phone, and that is never sent to Karo or to anyone else.
- Karo keeps no history of where you have been.
- Karo stores only the places you save (their names, where they are and their distances), so the phones you sign in on can use them. Only you see them.
- Delete a place at any time. Deleting your account deletes your places too.
Our privacy policy explains it in full.
Why a reminder did not ring: a checklist
- Is the task still open, and does it have the place on it?
- In Places, does the banner say place reminders are on? If not, it names what to turn on.
- Is Allow all the time chosen for Karo’s location, with precise location on?
- Is a battery saver stopping Karo in the background? Allow it to run.
- Is the circle too small for the building? Try 150 or 200 metres.
- Did it already ring for this place in the last two hours?
Set your first geofence reminder
It takes a few minutes: How to set location-based reminders on Android. Or get the Android app and see every feature.