Dash cams are now legal in UAE,
http://www.khaleejtimes.com/dash-cameras-legal-in-uae
The most important thing to do is stay calm. Dont let them goad you into driving faster, stick to a speed you're comfortable with. Sorry mr police man, I had another car up my ass isn't an excuse that will get you off with a speeding fine. If you can, pull to the right and let the idiot past. Don't get too close to the car in front either. It's bad enough if you happen to get rear ended but it's even worse getting sandwiched. There's a chance you won't walk away from it.
There is also the temptation to brake test them but just remember that if they're already up your ass over the speed limit and flashing their lights, there's a chance that they're not a particularly well adjusted or civilized human being and you could end up with a broken jaw next time the traffic flow stops. For some reason, certain people turn into big assholes when they get behind the wheel.