Hi,
1. XBMC with the VU+ addon can read EPG, switch channel and stream live-TV. I tried it once. Start was quite slow because EPG must be read but after that it was quite OK.
2. WD Live with a special custom firmware (I never tried)
3. Mediatiomb together with BH tuner server is able to stream live-TV over uPnP/DLNA and so quite a few uPnP-Clients might be able to show live-TV. (I never tried)
4. easiest way a little not so expensive E2 box
ciao