If you're doing any repair work on any modern car, I recommend having the appropriate scan tool. VCDS, at it's most expensive, is $300.
It's not just for changing the brakes. It's one of the most detailed and easy to use diagnostic systems from any manufacturer and it allows you to change long and short coding as well as actual trouble codes, both hidden and MIL-triggering.
An electronic parking brake isn't an overly complicated system - in fact it has fewer components than a mechanical system. As to your "what happens if the battery dies" question - are you planning on driving the car with the dead battery? Awfully simple to jump the car and release the brake. That's something I'd think you'd try before towing anyway, right?
I will add some actual engineering stupidity (or short-sightedness) to the conversation though:
The frunk release on my 911 is electronic. The engine compartment release is electronic. The frunk has no mechanical release.
The engine compartment has a mechanical release that you can reach from the rear wheel well, however most cars still have the cable in a coil taped behind the LH tail light - apparently it was supposed to be re-routed before sale. Oops.
This means that to jump the car you need to remove the tail light... Which you need to open the engine compartment to do.
So you have to jump the fuse block to get power to the release switches. Fun to figure out when stranded.