Is there a USB trackpad
You can still use wireless, but it has to be devices that use the 2.4Ghz receivers like the Logitech Wireless Touchpad.  It uses the "Unifying Nano Receiver" that plugs into a USB port.



I've used many wireless Logitech mice on KVMs (mostly Avocent) and all worked flawlessly.  The touch pad should be no different though I haven't tested it out because I don't own a track pad to test (I don't like them).