I never had a problem running Situations, and it doesn't feel unsafe to me. That's not a qualified opinion obviously.
There's a Situations thread here on TMO, maybe this has been discussed?

edit: https://pastillilabs.com/sonar/
Indeed, sonar is very powerful and therefore potentially dangerous.
As you already said, you should take care to uninstall sonar before uninstalling Situations.

But here's another advantage of using a phone OS which such a limited user base: who in their right mind would bother to even try to exploit this?