What can I use to view a mobile device remotely instead of VNC options which are too slow?

We have a dozen or so mobile devices for testing. Emulators in SDK's like Android's or Xcode have quirks. So, we use actually devices.

I've tried browser synchronization like browser-sync but that routes everything through a proxy.

I'm looking for a way to remotely view and control these devices from a desktop. I've tried running a VNC server on the mobile devices, but VNC is just too slow. Not to mention, the devices themselves lack any real processing power.

Any ideas?