Lost connection to iOS 8 simulator

Just try to "Reset the content and Settings..." in iOS Simulator, it works for me. Currently my Xcode version is 6.0 (6A313).

This should be a known bug of iOS Simulator after searching, you could try the above the solution to fix it temporarily. Good luck!

UPDATE: Before you try to reset the iOS Simulator, just quit (cmd + Q) and launch it, I found it works good in my simulator/xcode 6.1.1, too.

Simply Re-Run your project. No need to do any other step.