Here are a few announcements made at Google I/O 2015 -
Android M Android M (the actual name to be announced soon) is coming up later this year. Improved app permissions permissions wherein you will asked for context based permissions. Besides it bringing a lot of goodies with It as discussed elsewhere on this site.
Offline maps The Google maps is going to be offline now. Also a few apps like Chrome and YouTube have been promised to be made to use offline compatibility.
Polished Android Wear Apps will now be always on. Besides a few powerful new apps would be launched for Android Wear.
Android Pay Android Pay - the wallet service in line with Apple Pay is drawing closer. After a failed attempt with Google Wallet, a new format is being prepared for the new service which is believed to revolutionise virtual payment methods.
HBO NOW Ending the exclusive rights Apple has been enjoying, the HBO NOW has been announced for Android. Exact release date is yet to be announced.
iPhone compatible Google cardboard The Google cardboard will work with any phone now including iPhone.
Google photos app Google photos app will backup an entire range of your photos for free.
Google Now on Tap You can now bring up cards by tapping on home button. The service is being made more smarter.