External GPS?

I've generally found the GPS capabilities of my 5s mediocre. The map is always slightly delayed and it drains battery like nothing else.

Anyone using an external bluetooth GPS unit in their car? I was thinking about getting one and just leaving it in there matched to all of my family's devices. Then, in theory, the iPhone would have better GPS available and, hopefully, not drain the crap out of the battery.

Does this work in practice?

I got an answer from Bad Elf and will share here for posterity.

1. There are no power savings.

The Iphone will run its GPS in parallel with any external source and compare for best accuracy. So no battery savings.

2. Accuracy benefits are tough to define.

The Bad Elf GPS is about 2.5m accuracy (per their own statement, so probably add some distance). The iPhone is 5m+ accuracy according to the web.

3. The main benefit is quick lock without aGPS.

This is really unfortunate. The iPhone GPS is typically a bit slow and often inaccurate enough (especially in tight quarters like NYC, etc), that it can be useless or too late with a direction. Sadly it seems like you need a RTK GPS (which run over $2K) to get real accuracy and it wouldn't save battery life anyway.