Accessory makers are getting excited about the hidden - and undocumented - diagnostic port present on the Apple Watch. While leveraging this port is certainly innovative, making use of the undocumented port could have unexpected consequences down the line.
One accessory maker that is embracing this new port is Reserve Strap, a battery strap maker. The company had initially planned on using the regular inductive charger built into the Apple Watch. However, upon researching the diagnostic port present on the Apple Watch, the company discovered something interesting.
"We've developed and tested a completely rethought design that takes advantage of the 6 pin port underneath the band slide of the Apple Watch," the company wrote on the product webpage. "This port hadn't been deciphered by anyone until now but we've been able to make significant enough observations so far to warrant shifting our development focus to this new method. We're looking forward to sharing more design details and technical specification of this new Reserve Strap as soon as we can."
This comes across to me as a terrible idea for a commercial product.
First off, that port is undocumented. Playing with it could lead to all sorts of unexpected side effects. For a homebrew project it's fine to do things like this (at worse, if things go wrong and you invalidate your warranty or let the magic some out of your Apple Watch, you've only hosed your own Apple Watch), but for a commercial project, this makes me uneasy. It makes me doubly anxious combining an undocumented port with lithium polymer batteries worn next to the skin.
Secondly, there's the issue of Apple pushing a software update to the Apple Watch that changes the way the port works. Since Apple hasn't told accessory makers to use this, it's free to make changes to how this port works, which could affect how accessories work. While I don't think that Apple would do this out of spite, it could legitimately do this from a safety standpoint, and then your $250 battery strap becomes a $250 strap.
Another possibility is that Apple will open up the port to accessory makers at some point down the line. But for now there is nothing about that port that says "use me."
Finally, there's an issue of warranty. Since Apple hasn't told users to make use of this port, I'm certain that any issues arising from using it will not be covered under warranty. And you might even find that issues unrelated to the accessory might also not be covered.
And what about accessing the port in the first place? iFixit found getting the cover off the Apple Watch diagnostic port to be a struggle and had to dismantle the whole device and push it from the inside to pop it off. So just getting the cover off the port seems like a good way to chew up the metal finish and put some war wounds on a freshly minted Apple Watch.
Personally, I don't have a problem with breaking the "Tech Prime Directive" (which, in case you're not familiar with it, is "if it ain't broke, don't fix it"), and over the years I've taken many a device and "fixed" it until it's no longer working. That's the nature of homebrew. But I'm always reluctant to encourage others to follow my lead. So while I'd me more than happy to mess about with that diagnostic port myself and cowboy through any consequences, until Apple gives accessory makers the go-ahead to use it I'd also encourage others to leave it well alone.