"What I think is needed is some form of onboard primary radar like the military "target aquisition" stuff but at an acceptable price."
That is naiive in the extreme. Do you have any idea what 'military target acquisition radar' actually is? The acquisition cost, installation cost, power requirements and siting difficulties of even a simple cloud and collision warning radar in a SEP spamcan would be enormous. Let alone the CAA mod fees.... Let's just say tens of thousands of pounds.
You have to realise that all the silicone chips in the world won't be enough to protect you from other aircraft under VFR.
Remember, Visual Flight Rules mean just that!