Sounds a bit like
thisI think thats a great idea, would be possible as well, except for the fact the iPad doesnt have an IR port.
Getting the tv guide is easy enough from EPGs then you could just emulate IR button presses to get the set top box to change channel.
A more integrated model would require cooperation from the TV/set top box manufacturers which have so far seemed slow to integrate new technologies.
I still dont know why set top boxes dont integrate network media players. All the hardware is there already.