This is a new and un-used heated seat controller module, this part is normally located under your driver's seat.
This is the part Ford switched to after some of the early-S550-model-year heated seat modules would burn up around the ground pins.
Original price: $539.18
Sale price: $380 OBO...
If your Mustang is your only car, you might consider adding some functionality with a trailer hitch. Ford states that you can tow 1,000 lbs with either an EcoBoost or the V8 (this hitch is rated for 2,000 lbs if you're bold). That means you can tow a motorcycle/ATV, jet ski/kayaks, hitch-mounted...