The Fantastic Voyage is such an interesting idea for a videogame, it's amazing that we've not seen too many developers try and tackle it. Bloodrunner certainly tries, having a small vessel piloting the blood stream, and other dangerous areas of our squishy innards. Have a look at the trailer.
Now the iOS version most likely will not be out for a couple of weeks (Android and PC/Mac/Linux versions are all complete), so keep a look out on the App Store if what you see interests you. The sound and visuals look to create a unique immersive experience, even if the gameplay seems a little too much like the canyon runs in Rogue Squadron.