The current software was working, but had a rather high current when the controller was sleeping. The root cause of this behavior was that the SPI Pins, which are routed to the BMA Sensor, were floating.

With the Commit https://github.com/sulkith/BCDWristWatch/commit/1073f9e31e0a6df1e6c13bcc45b43ee938dedf17 this was fixed and the Watch now takes only 54.6µA in shutdown and will wake up on Wrist Tilt or double Tap