Been a fan of tvcatchup.com
for a few years now as it allows you to watch all of the freeview channels (and a few extra) on your pc. Now they have an android app, I've been trying it out for a few weeks and have had good results, the tv guide is especially good.
It works over wifi and 3g (but bear in mind it helps to have a data plan if you are out and about so you don't incur mobile internet charges).
Update: Also works on Ipad & Iphone, here is the link:itunes.apple.com/gb/…t=8
Check it out, it's free!