I managed to get a driver working for the IKEA TRÅDFRI Shortcut Button (article number 403.563.81)
And so here we go. I am by no means an expert in HE drivers so there might be some nasty quirks.
A code review would be appreciated.
The device should be put in pairing mode by pressing the link button under the battery cover 4 times.
If this driver is added after the device is paired you will have to run the configure command manually.
The Shortcut Button has to be activated before running configure by pressing the it once.
In some markets the article number seems to be 203.563.82