Beacons with an on off button are popular for product/app development because they allow testing of going into and out of range without actually physically doing so. They also allow the battery to be turned off to save power when the beacon isn’t being used for testing.
However, don’t solely rely on the button for edge detection. Actually do some tests at the edge of the detection area. Determine how your app behaves as it continually sees the beacon appear and disappear, particularly on Android where, unlike iOS in background, the OS doesn’t impose a period that a beacon has to be out of range before it’s considered seen again. On iOS, also test at the edge of detection when the app is in background or not.
We have recently added a web store category for beacons with an on off button.