General update:
Marshmallow support: You need to enable all dynamic permissions manually in system settings first. Please use nightly build or v0.02 release (which will land approximately next week) on marshmallow, older versions are likely to fail.
Further updates: I will switch to more regular updates (~once a month) and "official nightlies" soon™. Both will be provided through a F-Droid compatible repo.
BlankStore should display permissions the same way as Play Store does if installed as user app. If you install BlankStore to /system/priv-app, it will not ask anything at all.
Please note that on Marshmallow, permissions are not granted to apps targeting 6.0 at install time and thus are not shown at installation.
In case you are interested in helping with development, start by skimming through
android_external_Wearable and
org.microg.gms.wearable. If you have a test device with original GAPPS and Android Wear app available you can try the mitm proxy for android wear over tcp (used to connect emulator) - which is present in the android_external_Wearable repo - to get an idea of how the protocol works. Please join #microg on freenode for further development related questions.
GCM sending is not supported at all, but registering and receiving data is printed to logcat.