what is it?

2010 hhr ls - just bought - has a broken
item between the visors on the headliner.  
No sunroof.  It is a round plastic item with
what looks like a button type switch in the
middle.  Looks like the cover over the
center switch is gone which may have had
some info on it to help figure out what it’s
for. The center module that looks like it has
the switch on it fell out when I touched it &
it has 2 tiny wires attached to it.  It is just
hanging now.