This Chipotle blog entry describes things the best as far as I know: https://chipolo.net/en/blogs/chipolo-point-delay-and-google-find-my-device-app-update

Basically, in December, Google and Apple (and others?) came up with a standard on discovering trackers that are being used to stalk people. Because of the large iOS install base, Google has elected to wait for Apple to roll out that feature on iPhones before enabling the tracking device support on Android.

It’s called Tile, but they don’t have a replaceable battery.