A quick word of caution about an app that's just been released called VisionAssist.
The app has been developed specifically for those with low-vision, and claims to offer the same functionality and performance that you would expect from a handheld electronic magnifier, but with a few extra features and the advantages of being on your phone.
I had high hopes for this app, so was very disappointed to find that it was totally unusable on my iPhone 4. Or at least it is unusable if you need to be running VoiceOver at the same time.
For those of you who have tried using the latest version of Navigon on anything other than an iPhone 4S, picture the erratic and unresponsive behaviour that you experience from VoiceOver, and then multiply that by 5.
It looks like the video capture on VisionAssist is a major resource-hog, and as a result there aren't enough resources left for VoiceOver. This means that VoiceOver becomes horrendously erratic and unresponsive. It is impossible to reliably navigate page elements. VoiceOver focus randomly jumps from one page element to another, and when focus is on an element it is almost impossible to action a gesture (such as double-tapping on a button). Just once I was able to get the pause button to work by using a split-tap. When the video was paused, VoiceOver became more responsive, and I was able to use some of the controls (such as going to the settings page). Despite many attempts, I have not been able to activate the pause control again.
The only way to get my iPhone back working properly was to kill VisionAssist via the App Switcher.
This lack of responsiveness from VoiceOver when using VisionAssist seemed to be a lot worse than what I have seen with Navigon. With some patience and use of the split-tap, I am still able to use Navigon. This is not true of VisionAssist. The app was unusable, and it made the iPhone pretty much the same until the app was killed.
Based upon my experience, I would suggest that anybody with an older device avoid this app for now. I am in contact with the developer, and hopefully he will be able to address this problem.
I do not know if this problem would be present on the more powerful iPhone 4S. I do have a promo code for the app, so if a 4S owner would like to test and report back, please contact me.