You can score a free eye test every two years paid for by Medicare, but many of us don't bother. OPSM Eye Check is a free app that performs basic eye tests and gives you some indication of whether you should stop procrastinating and get a proper test.
The app tests for near distance, distance, constrast sensitivity, astigmatism and colour vision. To complete the full suite of tests, you'll need both a phone and a tablet; the distance vision test only works effectively on a larger screen. It's not a substitute for a proper eye test, but it's a fast way to check if there are issues you aren't aware of.
The app is a free download for iOS and Android.
OPSM Eye Check [iTunes]
OPSM Eye Check [Google Play]