At the very least invest $10-20 in a lock for your coupler. You can also buy keyed locking pins for your receiver. Here's a picture of the lock I'm using, made by Master.
I'm not terribly confident in it, but at least it's something. After suffering a house break-in in February (after updating doorknobs and installing deadbolts), I wish I could buy locks that would put shrapnel into anyone who attempts to break in.
In the picture, the lock is the round silver thing through the coupler latch. It's released by using a key on the square part and pulling it off the shaft:
The coupler lock pictured works to prevent the latch from being raised whether coupled to the TV or unhitched. There are some pretty stout locks out there for use when you are unhitched. My guess is try not to look like the easiest target!
Hope this helps