With iOS 9, iPhones know when to switch from weak Wi-Fi to cell data

There's a connectivity problem with Apple's iPhone and other iOS devices: If you're near a Wi-Fi source, they'll cling to that source even if the signal is horrendous, effectively killing your Internet.
In iOS 9 beta, this problem is fixed with the Wi-Fi Assist feature, which will "automatically use cellular data when Wi-Fi connectivity is poor."

See also: The 15 best features of iOS 9, in GIFs

Turning on this feature might result in a higher phone bill, but could be a life saver when it comes to working without interruption.

The feature was discovered by 9to5Mac Thursday, along with a number of other new goodies when iOS 9 was released to registered developers. Highlights include 15 new wallpapers, radio station Beats 1 and Apple Music support in CarPlay and Wi-Fi Calling support for AT&T users (previously only available for T-Mobile customers.)
iOS 9 is scheduled to launch this fall for iPhone 4S and up, iPad 2 and up, and the fifth and sixth generations of iPod touch.