I'm thinking about getting a digital inspection camera for use primarily in auto repair but also for other things as well.  

It has to have a small enough camera end to fit into a sparkplug hole.  I don't have to have super high resolution but I want it to be good enough to have useable video of footage to see what's going on in tight places.  

Got any recommendations?

Mike Busch of the Savvy Aviator would tell you to get a dental camera.  There are a number of excellent dental cameras that originally cost many thousands of bucks for sale on eBay for a hundred or so.  I bought one and it came with a screen and printer (which I never used).  The camera is excellent, and it is small enough to get into spark plug holes.  i plug mine into a laptop.  Works great.  When I first got it, I set it up in the office and told my coworkers this was the new corporate dental plan.  I only got one customer.