I rather like the idea of having an FPS/RTS/MMO hybrid, where the TV is you in FPS mode, doing quests and gathering materials, and the touch screen is your base that you build while you're out and you have to defend it from other players. You can build at any time, as long as you have resources.
Very cool. I'd also like to see some multiplayer coop version of this. Maybe one player is playing the overall strategist/RTS player, and the other player(s) on the main screen are actually assisting with the orders.
So for instance the Subscreen user might want to assault an enemy stronghold, so the Wii Remote player ((s) in split screen) could move with the AI squad to assist. Or just wander off and do their own thing in FPS mode but it would be better when they worked together or else you might find yourself alone.
In fact, thinking about this, there's a shit tonne of games that could work with this asynchronous gameplay. Will allow tried and true genres to get a bit of a freshen up!