Um, erm... YES!
So to clarify - Our servos only work with our EFISes and vice versa, so you couldn't hook up one of our servos to the Navaid controls.
But, as Mel said, you can connect just one servo to an EFIS an use it for altitude hold and altitude change (one neat feature of even the most basic Dynon autopilot is that it can fly to a new altitude once engaged). It won't "interact" or communicate with the Navaid autopilot, but they can co-exist.
An EFIS-D10A plus a servo ($750) will start at $2950.
Mike