A pocket sized, dual-band ADS-B receiver has just been released by ForeFlight called "Scout." This may be one of the smallest off-the-shelf solutions available for inflight weather and traffic for use exclusively with ForeFlight's mobile mapping software.
Dual ADS-B antennas are integrated into the casing and the unit is attached to the aircraft window with a suction cup mounting system. There is no software to download, nothing to configure--just plug into a USB power source and it communicates with your ForeFlight display via WiFi. Available at the ForeFlight booth or Amazon for $199.