This EPIRB is smaller than a cell phone. The signal is satellite relayed. Not dependent on a cell phone tower.
http://www.westmarine.com/buy/acr-electr...EbK3xoCntzw_wcB
Here's a smaller one that can be operated with one hand.
http://www.westmarine.com/buy/ocean-sign...Recs-_-MB-_-PDP