Mt friend Hasan's PHD project is the build a flexible RF front end for public safety radio's. In the US (and I suspect many other countries) public safety radios operate on a diverse set of frequencies. This creates problem for people trying to design radios that can operate of the range of services using these frequencies.
Hasan is working on a RF front to solve some of these problems. As part of this work he is build a demonstration unit that operates on several different frequencies. There are several parts of the radio that need configuration information via a SPI interface. He is using a gumstix computer to do the control and user interface.
Here is an overall picture of the unit. Since it is based on evaluation boards, it seems kind of large for a handheld unit. I'm certain that professionals could create a compact unit based on his work.
Here is a photo of the gumstis mounted on the front plate and the LCD touchscreen panel used to change the operating frequency.
Finally, a side view to give you an idea of how the gumstix is attached. He used a threaded rod to stack the gumstix boards and attach them to the plexiglass.