I've sat on my Note 3 (sans any type of case) more times than I can remember, and have never even so much as scratched it.
The rear pocket in women's jeans might be able to accept an iPhone 6, but only if the woman's rear isn't present at the same time.
It's interesting that "cargo" pockets, located on the side of the pants at mid-hip height, are popular right now, because that's a much better and safer place for a phone than the back pockets.