I would be delighted to make more money during inspections but I'm stuck on lack of overall value to home buyers for extra services. Sewer scoping and infrared cameras are recent additions.
Before I was in the home inspection business our inspector suggested a video of our sewer pipe which cost $400. Got a nice view of a paper towel. The problem with sewer scoping is that the line may be fine today and burst tomorrow due to frozen ground or a tree root. Instead, I recommend sewer back-up insurance, and main line sewer and water insurance. These are very inexpensive. If all the toilets flush nicely, you're probably OK.
Infrared cameras show heat loss through obvious penetrations: like above, under a doorway. Water is much harder to detect because the camera just shows temperature differences. I find it much more useful to look for actual water damage inside and the usual suspects outside: leaky gutters, bad grading, downspouts draining to the foundation. Also, our liability increases with inaccurate assessment of photos or not having pics of every wall: one poor inspector lost his business because he didn't scan one wet wall. (See also my ASHI article in a previous post.)
We should also talk about lead testing. A portable x-ray machine is used (x-rays bounce off of lead) and the test costs about $1000. Lead paint was banned in 1978 so give it a year to get used up. So, any house built before 1979 probably has lead paint in it. And it has most likely been repainted with latex paint so touching it isn't a big problem. Renovators will do scratch tests for lead paint before they knock down walls or replace windows. Therefore, the main thing is to not be around during demolition and check to see that HEPA vacuums were used during clean up.