How do you connect your pucks to the world?

I missed this one:

Is it possible/"allowed" to reuse other BLE Service UUIDs for custom data (Light,Mag,Temp, BTN state) ?

Yes, it's possible, but you'd get in trouble if you shipped a product that did it. It's not going to interfere with anything, but there is some small possibility that some other software might try and 'claim' your Puck. I definitely wouldn't lose any sleep over doing it in my own house though :)

There's also a 16 bit UUID for 'custom data' or something (I can't remember the exact name) - but I'm pretty sure you could just dump whatever you wanted in there.