I hope this is not to much off topic. But I hope it could help other users to activate the android tablet with a motion sensor.
1.) Install “automagic” on the tablet. I think there is only a paid app version, no free one. But cheap enough to test it 
2.) Add a flow in automagic (see the blue activated flow in screenshot)
2.a) Add a trigger for http-requests. This will start a simple http-server listening on the port and path.
Set the path and port you want to use.
The complete URL to call this is shown below (with your local IP). Use this later in Homey.
2b) Add the Logic to activate the display and call the App-Link.
I had to try a little bit selecting the homescreen link. Perhaps you have to create a new link from automagic. I can’t remember. Just try…
Then the flow should look like this (with additional check if display is off or on).
3.) Add the http request in Homey:
Install the app “HTTP request flow cards”.
Add a flow reacting on the motion sensor.
In WHEN part add the trigger of your sensor.
In THEN part add the http request:
You can test the flow and the tablet should activate the display (and start Homey link if set right in automagic).
