I've been trying to figgure out efficient methods of long-range communication for my robots. I have solved my dilemma by utilizing a mini-atx board and a cell phone connected via serial port. I think this is very effective, as I can run x86 linux code, have a fully functional robot, with ip connection/security abilities. There are some bandwidth limitations (9600 baud), however this should be easily overcome with the next generation of g3 cell phones.
Basicly, its linux running ppp to a cell phone/modem via serial port. Simple, yet effective, and gives global roaming abilities for the price of a throwaway phone.
I also believe that this solution far outweighs any other radio solution. There is no amature license involved, or expensive short haul radio solutions. (99$ and up for most..) when more can be accomplished with a 29$ cell phone. (And you can call people when not usuing it as a tty modem!).
Also, the included internal battery gives around 4 hours run time, or up to 2 weeks on standby!
However, the most important part to me is to be able to utilize my robot(s) as an directly attached web/network device.
Currently, the device boots a compressed filesystem from a floppy, that is removed afterwords, and the os/control software runs from a standard ramdisk. Currently there is a cut down version of apache, and limited java capability. Additionally, by utilizing the network connection, the robot can mount drives of any size via NFS, providing almost limitless computing/storage abilities.
Other possibilitys? Heavy duty processing can be acheived with the use of remote clustered servers. PVM based sumo anyone?