The way miniaturization is advancing I would think that soon manufacturers would offer a cellphone that would allow a PLB feature to be included with the service. Since most people carry their cellphone constantly they could have a PLB right there too.
If I had my preference I'd rather have that than a built in camera.
But like I said with the way miniturization is coming along we may soon have all of that in one hand-held instrument. Be careful don't lose it.