Hmmm... Not a bad idea at all - I have done several hundred real estate tours where no on was around (we have keys to the homes like the Realtors do)... We have never had a problem - At all, but I do see what you mean and the need for this. We have worked out custom pricing agreements for a few companies with contacts which should always be looked over by a professional.
The best thing you can do is have a professional attorney look over your agreement... They will often find things that you would never think of(some laws are state or region specific). It is expensive, but if you are going to rely on a contract to save your butt, you better make sure that it can do just that. If you want to save money, don't go the old pro that charges an arm and a leg - Look for a new attorney that is fresh out of law school as they will usually charge a lot less.
Hope this helps!
One thing that we have provided some of our clients with is a form that they use at the time of each listing that states that neither my company nor the real estate agency is responsible if a criminal uses the virtual tour or online photos to plan and commit a burglary. - That may be something you want to consider as well... Many franchise companies are already using something like that as well to cover them - If they are not, then you might want to suggest it to them.
Virtual Impressions Inc.
Real Estate Virtual Tours and Floor Plans