A few months ago, I wrote about my reverse engineering attempt to Logitech Unifying devices. Back then, I concluded my post with big hopes on the future after receiving a document with some part of the specification of the HID++ 2.0 from Logitech.
A couple of weeks ago, some of my summer work has been merged to UPower, adding battery support for some Logitech devices.
A year ago, I bought a Logitech Wireless Solar Keyboard K750. I'm particularly picky on keyboards, but this one is good. It has an incredible useful feature: while being wireless, it has no need for disposable or rechargeable batteries, it uses solar power!
My problem is that there's obviously no way to know the battery status from Linux, the provided application only working on Windows.