If you just want telemetry data -- HUD is prohibitively expensive and I know of no existing hardware that will give you a HUD built into sunglasses or whatever.
The other thing with telemetry is that most people will use it pretty much only for delivering alarms or logging maximums -- in which case voice and an LCD is just fine.
By having a "speak" button on the dashboard system you can "request" data to be spoken only when you want it -- for example if you want altitude you can press the speak button twice, if you want speed, press it once, if you want Lipo voltage, press it three times. Other than when prompted, the speech system remains mute unless one of the preset alarm thresholds is exceeded.
Simple, effective and easy to implement.