The best replacement for trackpad is trackball.

The best alternatives to trackpad are rated as following:
★★★★★  trackball
★★★  magic mouse
★★★  touchpad
★★★  mouse
★★  trackpad
★★  mouse ergonomics
★  mouse imac
★  mouse apple
★  mouse carpal tunnel
★  trackpoint
★  wacom
  wacom bamboo
  mouse photoshop
  mouse mac
  apple touch pad
  trackball blackberry

Your alternative for trackpad is not listed? Suggest!
Speaking about trackpad, one probably shouldn't forget about macbook.

Other search terms related to trackpad and their ratings are:
★★★★★ macbook
★★ keyboard
You have in mind a companion for trackpad and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of trackpad in all years. Click on graph for more.
trackpad
trackball
magic mouse