Supercomputers are big. Even when idle they still require lots of power and cooling, so ideally you want your supercomputer to be 100% utilized all of the time. That's why most supercomputers are "over-subscribed" and have batch schedulers (moab/torque, PBS, LSF, etc.). Users submit jobs, and the scheduler goes about placing those jobs on the supercomputer in a way that keeps utilization as close to 100% as possible. This means that typically when you submit a job it will not run immediately.
If your cellphone "out in the field" is relying on a supercomputer to do calculations, you probably aren't going to want to sit there waiting the minutes/hours/days it might take for your job to make its way through the queue. So you have a few choices: Make some sort of system reservation and only use your phone during the reservation time (probably not practical when you are "out in the field"), configure your scheduler to pre-empt currently running jobs in favor of the "cell phone" jobs (this might piss off non-cellphone users), or dedicate some or all of the system to doing nothing but being available for cell phone jobs....and the portion you dedicate will have to be enough to cover all of your cell phone users.
The last option is probably the best in terms of making sure that there is always supercomputing resources available for the cell phone users, but this undersubscription will cause your supercomputer to sit idle when field work isn't being done. So suddenly you are paying to power and cool a supercomputer that is sitting there waiting on the user to do something.
Supercomputer companies are slowly working on making supercomputers "greener", i.e. requiring less power/cooling, the ability to power off cpus/nodes/frames when not in use, etc. But until this green technology is perfected paring supercomputers with cell phones seems like a very inefficient way to do things.
