If you want to put your iPhone anywhere, and I do mean anywhere, check out the Cellphone Armor BodyDock System from BodyDocks. They use an extensive system of magnets (hence the name, ) that includes a rugged case, assorted magnets, security tethers, and more.
These components work together to allow you to stick your iPhone on your clothing, refrigerator, purse, lanyard, automobile dashboard and really just about anywhere you can think of.
You do NOT have to worry about magnets destroying your iPhone. Phones use solid state, i.e. non magnetic media, to store information. You should keep magnets away from floppy disks, traditional hard disk drives and CRT televisions, but your phone should be safe.
Still, these are powerful magnets and you don't want your fingers to get caught between them, so read their caution statement on their website and literature.