Technology is no substitute for technique
The problem is that no "technique" actually works. As has been written a million times, a target on a genuine collision course is a stationary point in your field of view.
The best one can do is play the probabilities in one's favour.
The "Mk 1 eyeball" so beloved of the proverbial ex RAF navigators who write the training literature, doesn't work, and never did work. Not in cases where there is a
genuine collision course.
Fortunately, due to the way flying is trained, it is not too hard to improve matters drastically.
Flying well above 1000ft, say 3000ft, reduces the probability more than anything else - by at least an order of magnitude. So much so that there have been no UK midairs (TMK) above 2000ft - ever.
Flying at weird levels, say 2300 or 2700 or 3300ft, reduces it by another huge amount - because most people who fly "high" fly as they have been trained i.e. at 2000ft 2500ft or 3000ft.
Be conscious of aerodrome circuits when flying enroute. Get a decent GPS which shows the ATZs and even when flying an accurate planned route, give these areas a wide margin. Another order of magnitude improvement?
If you have to fly low, e.g. taking pics of your bird's house, or departing or arriving, have all the lights on. One is far more visible in a near head-on situation when the landing light is on, even during bright sunlight.
TCAS would be great but until Mode C is made mandatory it will be of limited usefulness for avoiding actually possible collisions, versus the cost of the proper active system - £10k+. And I suspect a huge % of the low level bimblers don't have a transponder or don't switch it on, anyway, and if you fly high, there ain't nobody there, more or less.
Personally, I don't worry about this.
The circuit remains the dangerous place. The only time I do overhead joins is when ordered by ATC. At AFIS or A/G airfields I ignore the "overhead RH circuit" default instruction and if he reports no known traffic I tell him I will report downwind / crosswind / long final. But I must confess I wouldn't fly to Stapleford (or some other totally mad free for all place where people cut you up left right and middle) on a sunny Sunday
If you have an autopilot, use it to reduce cockpit workload and look out of the window - one day you might actually spot something.
If you have a GPS, use it to reduce cockpit workload and look out of the window - as above.
But don't bank on spotting the one that might get you while flying at 1000ft.