Mobile broadband users share data plans

ITEM: A new app enables mobile broadband users to share data plans with neighbors and passers-by in need of connectivity.

The app, called AirMobs, was designed with the idea of allowing users who are maxed out their data plan for the month, unable to connect to their service provider or unable/unwilling to pay for Wi-Fi in a coffee shop to tap into the data plan of a nearby user (voluntarily, of course).
 
AirMobs works on a tethering principle – it connects your device via Wi-Fi to other devices in range running the app, and uses that device to connect to the Internet using the data plan. Users choose how much of their data plan they share, and get credits per kilobyte shared that can be used when they need to make use of the app themselves to connect to someone else.
 
New Scientist explains further:
 
AirMobs runs in the background, regularly checking the phone's battery life and the strength of the cellular connection. It also detects movement, as the signal is more stable when the phone is stationary. When conditions are right, the Wi-Fi transmitter switches on automatically, and others can then connect.
 
Eyal Toledano, who developed AirMobs at the Massachusetts Institute of Technology, told New Scientist the app has been successfully tested, but hasn’t yet released it to the Google Play Store because cellcos might complain.
 
Undoubtedly they will. Many cellcos specify in their terms of service that sharing data plans with third parties is not allowed (outside of an actual data sharing plan, of course). And AirMobs complicates things by technically acting as a reseller (which is also prohibited in most T&Cs).  
 
It could also be illegal in some countries. A number of countries consider Wi-Fi piggybacking (i.e. using your neighbor’s unsecured Wi-Fi) a criminal offense, either because it’s considered theft, or because of the potential for criminals to use other people’s Internet connections for malicious activity. The fact that AirMobs is 100% permission-based may be beside the point, as far as the law is concerned.