Hardware

The x220t supports 2 fingers only, as do other wacom touch-enabled devices (bamboo, Intuos 5) and many built-in serial tablets in other tablet computers. The Apple trackpad supports more touchpoints (can't remember, 10 maybe?). Note that behaviours aren't the same, the x220t and other built-in devices are direct-touch, touchpads are by their very nature indirect touch devices. Be aware that plenty of tech specs say "multitouch" when they only support dual-touch.

My Asus Zenbook's Elantech touchpad for example supports multi-touch properly - two finger scrolling, three finger window moving and maximize/restore via pinch, and four fingers brings up Unity's Dash.

Note though that there is another variant used in some Zenbooks from Sentelic, and multi-touch support for that is only in some git repositories, whereas Elantech supports lives for example in the Ubuntu 12.04 LTS kernel.

How 'bout this?

http://www.ideum.com/products/multitouch/platform/features/

Curiously, "Linux version available in March 2012". I have no idea what that means exactly.

The Apple Magic Trackpads are great because you can add it to any existing computer setup. It is my recommendation for a multitouch trackpad.

Multitouch touchscreens are a different story. Unfortunately, I wouldn't "recommend" any touchscreens you can find on the market today on traditional laptops or monitors. I have heard of monitors with a newer eGalax touchscreen that supports five touches, but I haven't played with one to be sure. The best touchscreens are actually found on Android tablets. They tend to have the Atmel maXTouch chip, which recognizes and tracks many simultaneous touches. However, you have to figure out how to get a Linux desktop running on them first, and they aren't really designed for that.

I personally develop with a laptop with an N-Trig touchscreen. It does a passable job for development purposes, but it often drops touches or emits touches that don't exist.