Hunter has now a bit of everything (process attach, variable diffing like in pysnooper, env var activation, breakpoints, thread support and an api to build stuff on top) but without going overboard with overenineering (like serialization, storage or sql). For most intents and purposes it should replace every other tracer tool.
There's also a work-in-progress cookbook with unusual stuff: https://python-hunter.readthedocs.io/en/latest/cookbook.html