Yes, smartphones can be fun, no doubt about it (Flappy Bird, anyone?). But there's more to them than that. Take EyeNetra, for example: this young startup has come up with a smartphone-based service that offers on-demand vision tests. With Blink, people don't have to pay a visit to the optometrist to get a routine eye exam -- it comes to them. The newly launched service isn't meant to replace any optic emergencies that may arise, however; instead, it simply provides a test to determine if someone needs prescription eyeglasses.