I worked with someone that did this...she was a reflexologist and did it as an add-on
I have received many treatments.
Although I am not totally "sold" on the service, I did experience some beneits, it felt neat, and she had many regular clients that received the treatment at $30/session
I looked into bringing the service into my biz, but decided against it - it can be messy, I didn't like having to dump that gross water; it's time consuming (although not real work); and I think it can look kind of gimmicky.
I like your idea of bringing in on as a complimentary or for an event. It could be paired up with something else as a package - especially if you offer any other "detox" type service (like a wrap).
I used to do these. Talk about barf. I couldn't clean them out they would make me gag. Nothing makes gag! The floaters in these and the poop brown water makes me vomit. everytime.