I know its not proper medical research, but when my daughter was little, she often used to be a 'patient' for medical student doing their exams. She has CF, but was very well and didn't present with the usual symptoms at that time. It was quite fun. A very lively 2 year old bombing around the room, while the students tried to examine her and find out what was wrong. They would beg me to tell them what she had, but of course I couldn't. Once they had finally figured it out, I could then educate them on the condition, as I always knew more about it than them.
We used to get paid expenses plus a bit extra and some treats for her. Unfortunately, we had to stop, as she got to the age where she would tell them immediately what she had lol.
She also tried out new treatments, which were coming thick and fast at the time. We had to sign all sorts of forms to do so. We didn't get paid, but felt it was for the good of all CF patients. All of those drugs are now mainstream treatments for people with CF and I like to think that she saved lives by being one of the first to try them.
I also think that early access to the drugs have made a difference to her, as she has far outstripped her 'use by' date and is still going strong at 31.