How to put Google Nexus 7 securely in my car for use as sat nav? I know this question isn't about Android per-se, but about an Android device no less.

I recently got a new Google Nexus 7 tablet.

Now, I'd like to use it as car sat nav, but I couldn't find a decent holder for my car. I'm using a car power strip that also has two USB sockets acting as power outlets for USB devices. Powering the Nexus is no problem, so I don't need a holder/cradle, that supplies power to the tablet.

I was considering building it myself out of a dock or something, but even that I couldn't find. So, how should I put it in my car then? Should I just build myself a car-dock for it?
You can construct a mount out of something like Sugru.  Your mount will remain stuck to the dashboard and you would have to make it in such a way that the Nexus would slot into it.

For the elimination of doubt: I don't have any association with Sugru.  I use it to mount my iPhone on the dashboard.