Radar Display in rear view mirror?

Ok, I want to have my radar display show through my rear view, i know how to extend the wires but what is the trick to making the glass one way?  is the backing scrapped off where the light needs to show through or is professionally made one way (two-way i guess depending on where you look) the answer?

Thanks in advance!

I did something similar to my rear view mirror, I put my led for my alarm behind it. It should work for your radar to. I found a spot were I was going to mount it, and used a q-tip and some adhesive remover (auto magic no.40) am sure some thinner would work to. I had some vinyl sticker with litte holes just big enough to show the led. I used it as a templete and rubbed the remover till the light gray was gone. It was a little time consuming but the finish product looks great. still looks factory. 

beyond - do you have an pics of the finished product ?

i was considering the same thing, with mounting the sensors for the radar just behind the front grill and inside the rear brakelights

Where did you buy the two way mirror?

Matt