it depends on which FW it does support! for example SBRotator used to make my IOS 4 go to safe mode before sinful uploaded the latest version.
as for IOS 4, the only apps that didn't make my device go to safe mode are: installouse, iFile, Appsync 4.x ...
check the list that sinful stated in a thread posted on the main page to know which apps support IOS 4 on the repo
---------- EDIT ----------
here is the link of the thread: Check In and Tons of New Updates on the REPO! - SiNfuL iPhone