Tyre Pressure Sensor

[Big Gags]

When I was wiring up my reverse lights today I noticed that up under the rear RH corner of the car there was a small electrical box and when I looked on the side of it it says that it's a tyre pressure sensing unit.

It looks pretty neat and I'm wondering if this is a factory item or if the previous owner had it fitted as aftermarket (I've never seen any tyre pressure display so I am guessing aftermarket but who knows??). I will get out at some stage and get a photo of it to post up but any info would be appreciated!!