Durring the 80's the C64 was in regular use as a military weapon. It was perfect as a rugged combat computer.
The PDA thing is something I have been thinking about, there are lots of companies building such devices. I have some concerns about carring such things into combat. Increasing the potential of badguys getting hold of the device and it's content. A way to make it self distruct, if the user gets killed, would put me more at ease. To jepordize the mission or other team members lives for a PDA Hmmm!
Just my thoughts