Note: This is a bug in Android's native geolocation implementation. I can't speak to what happens on other platforms. However, I get the feeling that the bug is symptomatic of the JS implementation so it might very well exist on more platforms.
Description: When watchPosition is called, it first calls getCurrentLocation (resulting in a native call to getLocation), then makes a native call to addWatch. In Android, addWatch callback ids and getLocation callback ids are stored in separate data structures. The bug I'm seeing is, when I call clearWatch before the watch operation's implicit getCurrentLocation callback is invoked, the watch operation is removed/stopped in native, but the corresponding getCurrentLocation operation is not. This is not compliant with the W3C spec, which states that that no further callbacks for the watch operation should be invoked. Worse, this causes a bug on Android where GPS is never shut off! clearWatch stops the location listener iff callbacks.size + watches.size == 0, and so if the callback hadn't been invoked yet...
(Actually, skimming back through the code, I'm not seeing anywhere where the location listener is stopped after a getCurrentPosition. Which may be another issue... not sure.)