I've tried the current, supposedly iOS 7 compatible version of TomTom with my iPhone 5s, and invariably if I deviate from its route too much it just stops the voice instructions. I've used it for years on my iPad 2 with no problems...haven't used it on my 2 since iOS 7 though, so I'm not sure if it's a general incompatibility with iOS 7 (or a bug in the program) or something specific to the 5s.
Apple's Maps works fine, so it's not my GPS hardware. (Actually doesn't do a half bad job, but I don't want to be reliant on data, and Maps can't pause the audio you're playing when it talks, it just fades it down.)
Apple's Maps works fine, so it's not my GPS hardware. (Actually doesn't do a half bad job, but I don't want to be reliant on data, and Maps can't pause the audio you're playing when it talks, it just fades it down.)