That Zenec system looks pretty good as an OEM replacement.
I've used iGo8 on my smart phone and its a nice Sat Nav package. The integrated Parrot bluetooth would be a good feature too.
There are a couple of things though...
1. Does it work with on screen climate control?
2. The buttons illuminate white rather than the RNS / RCD's red colour.
3. No one knows what it really sounds like?
4. The playback buttons look a bit naff.
I'll stick with an RNS510, but if it was about £400 and I was looking for a cheap alternative, I may consider it. I have a feeling that its going to cost much more than £400 though?!