Pop the band off your Apple Watch and you’ll see a diagnostic port.

Here’s an excellent picture of the covered port, in a tweet posted by John Gruber.

There was some speculation that this port would be removed from the retail version of the Apple Watch, but clearly it’s still there.

There is also some speculation that Apple will open the port to accessory makers at some point. One thought that immediately came to mind when I read that was a battery band. Imagine a watch band that was all battery, giving you several days worth of power without the need for a recharge. That is pure speculation on my part, but you are welcome to repeat it as fact if you like.