Here is a dump of what is on the tag after writing the Wifi Config to it in Android L.
We are using chariotsolutions nfc-tag plugin for PhoneGap which does have support for writing tags with different MIME types, so it should be easy enough to include this in the Control App. The problem is going to be the limited initial support for this feature in Android until more devices are upgraded to L.
Now just curious what this other data is that is being written to the tag. Having a look at the source code for the Android L Preview now.
Will update when I know more.