I found this is quite amazing value for a Multi-touch screen, especially at 21.5" as well.
MEDION® AKOYA® X54000 21.5" Monitor (MD20165)
21.5" Widescreen FULL HD Monitor
Screen Aspect Ratio: 16:9
Max resolution: 1920x1080 pixels
Response time: 2 ms
Dynamic Contrast: 60000:1
Contrast Ratio: 1000:1
2 built-in speakers
Included Touch Pen for proper text input
Have DVI-D in, HDMI, VGA in, Audio in, USB port (for use with touch function)
Have just used it for 30 mins, this screen is amazing, easy to setup. The screen quality is very good. The multi-function function only works on Windows 7, not MAC OSX. Very accurate touching, like on your iPhone, response rate is very quick as well.
The screen is glossy, only LCD back-lit but looks like LED back-lit. Picture is crisp colorful.
I do recommended this screen to anyone who is looking to buy an external monitor, as it worth every penny, especially the multi-touch function is absolutely fantastic