When all is said and done these aircraft are flying VFR and so it is down to the PIC to maintain a good lookout, now i know the limitations of the PA28 and can understand how this could hapen even when all crew are doing the best they can to keep a good lookout but all this talk of ILS/VOR etc is just crap it would mean more guys flying around "heads down".
the only bit of high tech kit that would be of use is the device that picks up the strobe lights of other aircraft and warns you of proximity to other aircraft,the CAA was funding reserch into such a device but what has hapend on this front i dont know.
The guy who taught me to fly kept a good lookout because in his youth failure to do so would mean a ME109 drilling 20mm holes in his back....as he said to me "a PA 28 or C152 can kill you just as dead"
So as one who flys VFR a lot what i am trying to say is the responsability lies with all of us to keep that lookout, for your safety lies in your own hands ( or eyes)