Windows Phone 8 has the GeoCoordinateWatcher which is present in Windows Phone 7, but it also has Geolocator, both of which perform the same function, i.e. allow you to 'watch' for changes in geolocation. I can't find any information about whether GeoCoordinateWatcher is deprecated, whether Geolocator should now be used - or the differences between the two.
Any ideas?
Simple - if you don't need or plan version for WP7, only for WP8, then use the Geolocator - it is better configurable than GeoCoordinateWatcher.
Or, there is another solution that I have used in my app, use Dependency Injection and implement common interface for your geolocation service, that will be implemented using Geolocator in WP8 version and using GeoCoordinateWatcher in WP7.