What do you mean by "control"?. You can send network traffic to a PC via the phone network tcp/ip (subject to their firewalls) or directly (via a WiFi or Bluetooth or infrared connection). However, once you do that, the PC is going to have to figure out what it's going to do with what you sent to it.
Customer surveys are for companies who didn't pay proper attention to begin with.
Logitech makes a mouse/keyboard application for the iPhone/iPod touch. It connects to any mac/pc with the appropriate software installed. I suggest you take a look at it for an idea of how an infastructure like that would work.