I've joked before about my
"Harbor Freight Industrial Proctoscope."
I believe I've used it more often on trailers than any any other household or professional job. Currently, I'm in the process of installing a new 120V outlet on the stove side of the kitchen, to accommodate DW's favorite induction cooktop. The job involves drilling a hole in the wall at the far end of a false-floor wiring compartment under one of the hanging cabinets. Without this camera, the job of snaking this wire would be three times harder.
Anyway, I wanted to mention that this unit is 20% off until September 2 ($75→$60), so if you ever thought you could use one of these, now's the time. I've had this unit for more than five years, and it has never given me a lick of trouble.