The separate screen and keyboard, similar to the Palm Foleo - you're describing the Celio Redfly. 8" screen and keyboard, looks like a small laptop, but uses the phone's software. Has a bigger battery that can also charge your phone (very handy).
I use it quite a bit to file flight plans and check weather - much easier than looking at the small phone's screen, especially as I get older and my eyes get worse!
Also works great with our company's Citrix server - 800 x 480 screen is much nicer than trying to view a windows desktop via citrix on a mobile phone.
Take a look at
http://www.celiocorp.com/.