Hidden trackers and AirTag mounts for theft recovery.
A tracker does not stop a theft, but it turns a lost bike into one you might get back. E-bikes are stolen often enough, and are valuable enough, that a hidden tracker is a reasonable addition for anyone who parks outside. The two main types behave very differently, and knowing which you are buying avoids disappointment when you need it.
Bluetooth trackers such as an AirTag or compatible tags rely on nearby phones to report location. In a dense area like a Frisco shopping center or a DART lot, that network is surprisingly effective, and the tags are cheap, last a year on a coin cell, and hide easily in a purpose-made mount under a bottle cage, inside a bell, or in the steerer tube. The downsides are that a thief's own phone may alert them to an unknown tracker, and that coverage fades in empty areas. Cellular GPS trackers report location on their own via a subscription, work anywhere with coverage, and often add motion alerts and geofencing; they cost more up front and monthly, and need charging or a wired connection to the bike's battery.
Placement matters as much as the device. Put it somewhere a thief will not look in the first minute, do not advertise it with a sticker, and consider a second cheap tag as a decoy. Pair the tracker with a good lock and a registered serial number; when a bike does turn up, police need the ownership documentation to act. A tracker is the last layer, not the first.