I am looking for apps that will help me locate devices by playing a sound on them, overriding silence settings and similar. Should be possible to use from web and other devices. Until now this is similar to what you can do with the web-based services from Google and Apple.
In addition, I would like that "friends" can give me access to "locate" their phones, that the channel can be used for other forms of communication, and that it can work locally (Bluetooth for example)
GPS location (like mention web sites) is of course nice, but it should be possible to restrict it.