Reverse engineering; getting an idea of what an unknown app might be doing, and where, so you can trace it back in the code. And so on.

Surely whatever RE tool you're using already has a memory viewer built in.

Hrm. As a half-bakes thought - if code handles sensitive data, making sure it is correctly obfuscated in memory?

This. I'd be nice to have a list of strings to monitor (ex: half of the ssh private key) and warn when they are found somewhere, to detect data exfiltration.