One I'm very interested in that I don't have the time or expertise to really tackle is single-lens photogrammetry (or photogrammetry in general). Right now there isn't a great consumer-friendly option that doesn't require custom hardware. Many online resources recommend specific lighting and high-contrast colors to get a barely-accurate scan.
Another similar-ish one that other people have started addressing is building a system that reliably detects photo/video manipulation (ie. photoshop & deepfakes). An interesting extension of that would be detecting audio manipulation in a video.