iSHSHit is a popular Cydia app which allows you to easily backup iOS SHSH blobs. This app has now been updated to bring ability for saving iOS 4.3.4 and iOS 4.2.9 jailbroken iPhone, iPad and iPod touch SHSH blobs.
You need to save SHSH blobs because if in the future you want to downgrade to any previous iOS version, only saved SHSH blobs will enable you to downgrade firmware. It automatically uses the Cydia On File service in the background, so it's a great way to ensure that your SHSH is stored by Cydia. iSHSHit also allows you to email your SHSH blobs so that they remain perfectly safe in as many email accounts you want them to.
Those who don't have a jailbroken iOS device, can use our tutorial on how to save iOS 4.3.4 / 4.2.9 SHSH blobs using TinyUmbrella on both Windows and Mac computers.
The latest version of iSHSHit is now available for download in Cydia through the BigBoss Repository.