This could in fact work.
All you need, is a Handheld device with USB-Host functionality (which most modern ones should support Samsung SGH-i900 Omnia does for example
http://forums.thoughtsmedia.com/688634-post10.html)
All you need now is to hook up the keyboard to the USB-port using a connector like this:
img src: http://img23.imageshack.us/img23/9190/auy1000atq6.jpg
The last thing you need is a software called USBInput:
http://www.teksoftco.com/index.php?section=usbinput
With all this, it should work to hook this thing up to a Windows Mobile Pocket PC. The costs are still way below a Bluetooth-Keyboard, but all the cables are of course a big downside.