In this flight, we tested SafeSky. SafeSky is a mobile app that provides traffic information. SafeSky collects information from 15 different sources (ADS-B, Flarm, OGN, SafeSky itself, ...) to construct a comprehensive traffic view. This traffic view is transmitted to the app via cellphone internet. Your own position is also transmitted to the SafeSky system via cellphone internet. So, the more pilots use this system, the better it will get.
There are a few caveats though: Cell phone reception, completeness of traffic data, and latency. Here in Austria, cell phone reception is usually very good. Even at higher altitudes at or slightly above ridgelines. That's because cell phone towers usually are situated on ridges.
However: There is absolutely no guarantee, that all traffic will be shown. So the primary way of
preventing conflicts is still to LOOK OUTSIDE. But a tool like SafeSky provides valuable ADDITIONAL information. Especially about traffic that is not (yet) visible to the eye.
The fully functional basic version of SafeSky is free. So everyone can give it a try without risk.