Sega has released quite a few iOS games so far. Just search the App Store for "Sega" to bring up lots and lots of various Sega-made titles. Many of those games are published by Sega and developed by other companies. The games that Sega has made are essentially all ports, or games that appeared on other systems first. That makes Sonic Jump, available today on iOS for the first time, Sega's first original mobile-only title. It's the first game Sega has developed specifically for Apple's platform.
Now, "original" may be a little bit of a stretch, as we say in the video preview below, because Sonic Jump is essentially Doodle Jump, only dressed up with Sonic graphics and sounds. That's not necessarily a bad thing, as it is always fun to run the little blue hedgehog around (even if, in this game, he doesn't really do very much running at all). But it does mean that Sega didn't go too far off the beaten path on this one. If you've played Doodle Jump, you know how Sonic Jump works.
The one exception is that Sonic Jump does have an interesting "stage" structure, which provides quite a few different levels to play through and then get rated on, with higher difficulties to chase all the time. That's a nice bit of innovation, but it doesn't really change the gameplay. Sonic Jump's tilt-to-move and jump mechanism is a well-traveled cliche on the App Store by now.
All that said, Sonic fans will like this one, and the game is fun and well-made. It's probably not quite worth the full US$1.99 purchase price, especially since the game has a lot of freemium features already cooked in. But my guess is that Sega will drop the price on this very soon, so if you'd rather not spend the couple of bucks, watch for a price drop, and pick up Sonic Jump when it's a bit cheaper.