Durable, Shockproof Computing?

trefoil asks: "My friend's father is a farmer who has to tend to his huge wheat fields for most of the day. He is looking for an option to have a full computer system on his tractor, however it bumps and jostles around a lot. He was curious as to what type of options besides pda's does he have, for something that can 'take a beating and keep on ticking'. Specifically what we're looking for is something shockproof, hopefully not to expensive, the less "moving parts" the better. Any ideas out there?" If such a solution does not exist that's exact to the one described here, how close can today's market get to a sturdy computing solution that could handle life on the road...or farm?