If you continue your efforts perhaps someday they will be less expensive, take standard lithium batteries and become more durable. I think we would all appreciate some improvements, beyond the recently intoduced models of PLBs.
Well, I really cannot allow that comment to stand without a response as it implies that existing PLBs are somehow deficient in durability, which I do not believe is supported by the facts.
I always find it interesting that every electronics manufacturer (not an existing beacon manufacturer) who has come to me and thought they could produce a less expensive PLB, smaller PLB, etc., etc., has discovered it's a lot more difficult and expensive than they figured. I am still waiting for one of them to come through. <g>
After a few years working on the standards that govern these beacons, I have a better understanding why this is so. PLBs will get less expensive and smaller and lighter as the technology available allows, but reliably transmitting to a satellite in orbit 22,000 miles up is a lot more difficult than you might think. Add a GPS receiver to the equation that has to operate while the beacon is transmitting on 121.5 MHz homing frequency and it adds to the design problems.
The idea that you could use "standard lithium batteries," assuming you mean something you can buy off the shelf in a local store, while still meeting the tough standards and design criteria to produce a competitive product, reducing size and weight and all the rest, is pretty far fetched. Actually, to a degree what they all use are standard cells, just not what you can buy at the local store, and they are assembled into the battery package that works for any particular beacon. A package in which the power supplied is only one design factor, and often not the most critical. That's one way costs are kept down. Military beacons get more exotic batteries, not necessarily "standard," and they pay for it in much higher costs. It's one of those things that on the surface seems to be so easy, but really is not. And, unlike the issue with selling razor blades, there's little financial benefit to a company having a proprietary battery, they don't make much, if anything, on replacement batteries since they don't sell many and the service life is so long anyway. With the reduction in size and weight and price, people just go out a get a new beacon. Most I have spoken with in the business would love to not be in that business, at least with regards PLBs, it's just an expensive customer service nightmare PITA for them. Standard batteries would solve that problem, but they are not very practical for PLBs for a host of reasons. Wishing for lower cost beacons is one thing; wishing for something irrelevant and unimportant in the grand scheme of things like this, that's losing sight of what's important, which is saving lives.
As for the rest, I think the proposed standards are plenty for most circumstances. The latest ACR PLB is waterproof up to 16 ft (5 m) for one hour and 33 ft (10 m) for ten minutes. How much more waterproof, (always at greater expense in both cost and likely weight and size) would you want it, and how would that benefit the typical end user backpacker, climber, boater, etc.? PLBs are already required to withstand six drops from a height of 1 meter after cold soaked to -30 degrees or -40 degrees C (depending upon class). That's pretty cold for plastic and electronics to withstand impact forces. Given that gravity accelerates it at 10 meters/sec/sec and the force goes up at the square of the speed (if memory serves me correct), which means a even slightly higher standard requires significantly more hardening at ever increasing cost, weight and such, how much more hardened do you want it? ELTs have to survive 40 Gz and a lot more abuse, but they are lots heavier and much more expensive in part because of that requirement. It already far exceeds a cell phone or sat phone or most any other piece of typical consumer electronic gear in these regards.
Leading (and often bleeding) edge technology military beacons are available that are smaller and much tougher, but they also are 8-10 times more expensive and there isn't the economies of scale necessary to bring that technology to the mass market at this point. What we are seeing today was bleeding edge tech 5 years ago and has benefited from things like cell phone technology in digital electronics design, so it does trickle down eventually.
We spend a good deal of time in these committees arguing over where to draw the line on standards, what's good enough, at what point do you reach diminishing returns or is it counter productive? There is rarely a free lunch, though sometimes technology provides for a means to do better without a increase in cost, and that's one reason such standards are reviewed on a regular basis, so when technologically it can be made "better" without adverse impact we can raise the bar. However, the bottom line is always that anything that increases cost reduces the number of beacons in the hands of end users and anything that makes it less expensive increases the number of beacons out there and that translates into more lives saved. It always a balancing act.
We also have to design standards that actually ensure the product will reliably save lives. Some standards that have existed could be met with a design that wouldn't work worth a damn in the real world. If the goal was just to produce a low cost beacon, a company who might be located someplace where saving lives isn't part of the corporate or societal culture could design a lower cost beacon that would pass a standard, but might not save lives. What is the advantage of that? This is a real problem in some lifesaving gear (not yet for PLBs per se).
Anyway, I have rambled on long enough. Just want to ensure anyone reading this thread doesn't come away thinking that PLBs aren't capable within reason or that there's no thought given to these issues or that the solutions are as easy to accomplish as they are to suggest. I don't know any company in the business who isn't trying their utmost to make their beacons smaller, better and/or cheaper, or preferably a combination of these features.