Just get the cost down to hand held GPS prices. Basic model GPS that is!
Your next challenge me-thinks.
The Doug Ritter PLB.
Competition, both against other PLBs and stuff like SPOT, will ensure that PLBs will be as inexpensive as they possibly can be, believe me. While it may not seem so if you just look at the retail pricing, we are already reaping the rewards of a traditional marine pricing environment (at least in the U.S.) where much life saving equipment is sold as well below normal margins.
There are a number of things which work against lower prices. First is the still relatively small market. GPSes sell by the hundred of thousands, not so PLBs. PLBs must meet some very stringent construction and performance standards, not so GPSes. A PLB requires considerable time and a large bucket of money to be certified by COSPAS-SARSAT, and then receive a time-consuming and expensive authorization by individual countries (the FCC in the U.S.) to be sold, not so GPSes. Moreover, the race to make PLBs smaller and lighter, and thus more appealing, also works against lower cost and smaller and lighter almost always translates into more expense, especially when small volumes are involved.
PLBs will get less expensive and there are efforts underway to relax some of the standards that might encourage this, but the newest and best won't be cheap anytime soon. Nor is there likely to be a D.R. PLB anytime soon. <g>