I jsut got a tablet as a gift and first thing I did was install the HBT app and BrewR. Haven't used it during a brew day yet but I played around with it and it seems pretty neat.
I use BrewR just to keep recipes organized and so if somebody asks what's in a brew I can tell them. The only other one I have other than HomeBrew Talk is called HomeBrew Calculator which has a lot of different options.