Do I need an iPhone to use a Bluetooth tracker?

It depends on the model. Find My-certified tags such as Apple's AirTag and most MFi-certified 4-packs are iOS-only, while Samsung's SmartTag2 is tied to Galaxy/Android phones. Tile (now owned by Life360) is one of the few brands reviewers note works across both iOS and Android. Radio-frequency beepers like Esky and Reyke need no phone at all.