Creating a live tile should be totally possible; we already know the API for that. Doing it in a way that won't wreck the battery life will take careful work, but is surely possible.
What I'm excited about here is a persistent background service that isn't subject to the app model restrictions. This can be used for things like automatically muting the phone in meetings (with exact timing, not the loose timing that the current background APIs give). It can also be used for things like making openVPN (a current project of mine) work on stock ROMs, which would otherwise be very difficult (technically possible if I can get the driver to load on a stock ROM, but a mess of hacks even then).
What I'm excited about here is a persistent background service that isn't subject to the app model restrictions. This can be used for things like automatically muting the phone in meetings (with exact timing, not the loose timing that the current background APIs give). It can also be used for things like making openVPN (a current project of mine) work on stock ROMs, which would otherwise be very difficult (technically possible if I can get the driver to load on a stock ROM, but a mess of hacks even then).