Cooking kidney beans in a slow cooker, how do I make sure they're safe?
I found this question interesting because I'd never heard of poisoning from red kidney beans before, and have certainly cooked them solely in the slow cooker without ill effects that I can recall, so I did a little internet research. Here's the most authoritative opinion I found: 


The US Navy Medical Corps thinks that cooking even at 80C/175F is insufficient, and may be more toxic than even eating the raw beans.


Particularly, I found this specific advisory in at least 4 internet sources, including this one:


  Beans cooked at 80 degrees Celsius, which is common in some of these
  cooking methods, increase the toxicity potential 5 times higher than
  eating raw beans.


This startling theory is never sourced anywhere; all of the sites I can find that mention it provide the information without attribution, even the serious medical ones.  Many use the exact same words.

So it's up to you whether or not you believe this; personally, with a possible night of stomach cramps on the line, I would probably choose to dump them in a pot for a quick boil.  On the other hand, I might consider what % of the soup is kidney beans and chance it.