Technology should gradually make this kind of thing a feature of the past. All but two of my companies trainers are equipped with "TIS"- an ATC radar-based traffic information system a bit like TCAS. It uses the same symbology as TCAS also. When it gets positional data from local ATC radar on other aircraft it sends that data to the aircraft with the system installed via the transponder. It is not all that accurate because the radar only sweeps so fast per cycle and the radar does not see aircraft below a thousand feet or so but it s a great aid to safety.

I keep the TIS display on when I am in the practice area and it really helps not only to make us safer, it helps me know when the danger level is getting high. I am able to put my attention on the other aircraft when I need to then pull it back to teaching my student when everyone is gone again. It's a great thing to have in a training environment.

When ADS-B comes online there will be another big improvement in anticollison systems for trainers. ADS-B combines GPS data with local radar data and beams it up to the aircraft. It sees everything the GPS satellites see which as we know is just about everything up there.