There isn't a single engineer on the planet that even remotely doubts the Batteriser will "work" as a boost converter and give you 1.5V output from a "dead" or "used" battery.
Well, I doubt it now, after the Indiegogo comment from one backer, that the voltage indicator on the Apple keyboard went from 39% to 87%, assuming 39% is still at a reasonable level above 1V (because otherwise the percentage would be wrong, because of the time left at this voltage), which is fine for many boosters (many can start from 0.9V and work below once running) and 100% is 1.5V or higher (because I would expect the meter to show 100% with fresh batteries). I have a Mac, so I could even use such a keyboard. Found a seller in Germany for cheap (EUR 40), well'll see.
Dave, if you have access to a Mac somewhere and if you want one, I can forward the keyboard to you for testing (I guess you will get a sleeve sooner or later). You could do a Garmin-GPS like test, but more professional, with multiple multimeters, one for the battery terminal voltage, one for the voltage after the terminal and one for the current: A servo motor which hits a key every some seconds, then measure the time until it dies. All automated by a simple Python script on a Raspberry Pi (with the help of the
Raspberry Pi2/3 logging platform for Voltnuts). The servo can be controlled from the Raspberry Pi as well, without any additional hardware,
as I demonstrated. Or maybe better, use an Arduino for controlling the servo and then use something like
Processing to send commands to the servo, read the multimeters, create a nice diagram and detect the key presses. Would be a fun weekend project to program and setup.