Here's the leather magnetic case I use.
I've been using it with my Droid X from July 15th, 2010, (launch day) right up until the time I upgraded to my Razr Maxx HD on October 24th, 2012 with absolutely no ill effects on either phone. The Droid X was carried daily for just shy of 2-1/2 years and my new Maxx HD for almost 3 weeks. I've been using the same holder everyday. I think it's safe to say you should be good if you use a case with a magnetic latch even with an iPhone.
The only thing I had on my "X" was a screen protector but my Maxx HD has been naked since day one.
Go for it!!!!