I work on mobile distributed systems, platforms, and apps. I'm advised by Professor Li-Shiuan Peh.
Current mobile apps are typically designed with a client-server model, where the mobile phone app (the client) talks to some server (sitting somewhere in the cloud) over 3G or 4G cellular technologies. Phones are quite powerful, however, and much of that local compute power is untapped.
We build systems that move computation that is typically done in the cloud, like sensor data fusion or location-based services queries, to the phones themselves. We take advantage of short range wireless communications between phones to reduce demand and pressure on cellular networks, e.g. adhoc WiFi for now, hopefully something better in the near future with wireless @ mit ;-)
Challenges we face include how to partition data, resources, and responsibilities across many different phones, how to make it easy to write apps using this new model, how to deal with mobility and intermittent wireless connectivity between phones, how to reduce energy consumption so that people won't uninstall these new kinds of apps, and more.