What is this and what does it do?

I bought a used 2009 Tacoma yesterday and I found this thing wedged behind the visor. The electric cable goes down the drivers side post between the roof and the body. It turns on a blue light when the parking brake is pulled on. What is it? What does it do? and where does it originally go.

Thanks

 

Aftermarket alarm antenna?

Looks similar to what I pulled out of my uncles Tacoma, his aftermarket alarm was draining the battery. Pulled it out and reprogrammed his factory remotes, did the white wire mod and added the glass sensor, bingo, factory alarm.

 

^^^ yeah this guy nailed it. I had an aftermarket alarm installed on my 02' accord and it had one of those

 

Thanks for the help

 

Looks like a remote start antenna.