Not a touch screen, but this is as close as having like a 'computer'. What I use for my music source everyday.
A 7in hardest monitor, with a pioneer single din for the main h/u(ipod integrated, aux, cd player)
My Apple tv 1st gen 160gb. Where I save my music videos, movies, songs, pictures, even you get on YouTube if you got a phone with WiFi hot spot(mainly today's Android/iPhone 3gs/4.) It's jail broken so I can use a composite cable on the component video output without having a converter.
Edit: next project is to switch out the hardest monitors I have and buy 9 nch monitors with HDMI/component input (i think lilliput is the companies name with those kind of monitors, but its $200 a POP)
All for an estimate of $300(just to round off).