I got an email the other day from a former professor with whom I used to work - and it reminded me that he used to have a lab that was used to calculate the amount of calories spent by the person inside doing a variety of activities.
In any event, it got me thinking - I could actually make this happen - depending on age/weight, heart rate, etc, I could figure how many calories can be burned by tickling alone. Off-hand - I gotta imagine intense tickling would qualify as a "moderate workout" like jogging on a treadmill (about 4 METs).
Imagine the possibilities. I'd quit my job, open up my own Tickle Clinics, help people lose weight and make some money.
Let that rant swirl around in your head.