Android M will come with native support for fingerprint scanning. You'll be able to use fingerprint scanning to pay using Android Pay, as well as unlock your device. Users will also be able to make Play Store purchases by authorizing them with their fingerprint. Usernames and passwords can be saved an authenticated with a fingerprint scan.
Google also announced that developers will be able to add fingerprint scanning support to their apps. Android M comes with a standardized fingerprint API, and an Open Authentication API.
Keep your eyes on the Android Central liveblog of today's Google I/O keynote for the latest.