KeyTouch is a Mac and iPhone app by Dutch developer Tom de Ruiter, it lets you unlock, lock and enter your password on your Mac via Touch ID on your iPhone. It's incredibly simple to use and easily one of the most time-saving apps for Mac.
Simply download the KeyTouch app from Mac app store, then the same app from the iOS app store. Once downloaded, follow the onscreen instructions from your Mac and you're done. Incredibly useful.