Unsanity provides (for free) a protection against a recently discovered security flaw in Mac OS X:
A vulnerability in Apple's Mac OS X results in a potential situation in which a malicious person could execute arbitrary commands on your machine, such as deleting your home directory, or doing other harmful actions. This vulnerability involves the use of URL "schemes". These are the part of a web address that specifies what program should be used to handle the address.
Paranoid Android can protect you from this potential vulnerability until Apple makes an official fix available. It does this by watching the URL schemes that are requested and delaying them until you've had a chance to say whether you'd like to proceed or not. If you know that the url that's being loaded is legit, go ahead, but if it looks suspicious, Paranoid Android gives you an opportunity to cancel it.
I'm confident that Apple is already working on the fix, but thanks to Unsanity for being so reactive and for releasing this for free!