If I really wanted a video, I find the ideal solution is to have 2 girls there. One does the recording while the other performs. The best part is that if you want some variety, they can switch positions :p
In one-on-one scenarios, I would go for the hand-held cam or a small mini-tripod mounted cam. Much easier to handle
With iPhones, I think the best is when you are getting a BJ, she is on top in CG, doggie, and some variants of missionary (when you are not lying directly on top of her). Otherwise, its much easier with a proper cam + tripod.