There's a difference between the stalking and phone spying. The former needs legs and an effort to travel wherever the stalking prospect goes, while the latter only needs the device and the prospect's phone. In stalking, you always need to hide, while in phone spying you just have to listen intently. This is also the advantage of phone spying because you are able to listen to the conversation unlike in stalking. Spying devices are for any telephone and mobile phones like the
useful Sony Ericsson's, Nokia's or Samsung's.
