TinyUmbrella was a popular SHSH blob saving tool that made downgrades and iOS restores possible. Unfortunately, Apple began closing the loop holes used, thus blocking the ability downgrade and re-restore. Saving SHSH blobs is still "useless", but semaphore, the developer, hints that that could change soon.
Previously, saving SHSH blobs let you restore regardless of whether or not Apple was signing the firmware. For instance, if you needed to restore your phone, but the latest firmware was not jailbreakable (ex iOS 8.2), you could use your SHSH blobs to downgrade to a lower firmware version, or simply re-restore to a jailbreakable firmware (ex iOS 8.1.2).
Details are limited, so we aren't sure what semaphore has planned, but for now, a beta version of TinyUmbrella with limited features has been released in order to iron out various bugs before releasing a version with "more admirable features". Those "admirable features" are likely going to make saving SHSH blogs relevant again. Semaphore hints at the upcoming features on twitter, and even discusses working with @iH8sn0w on an exploit he discovered.
I would not have updated TU if there wasn’t at least a moderately good reason to. So, no it is not useless to save them.— semaphore (@notcom) March 14, 2015
@matteyeux with what you know yes. With what you don’t yet know, quite the opposite.— semaphore (@notcom) March 14, 2015
While iOS 8.1.2 is no longer being signed, TinyUmbrella can save the SHSH blobs off your device if you're currently on 8.1.2 (so if you're on iOS 8.1.2, stay on iOS 8.1.2!). The beta is available now for both Mac and PC. We recommend that you save your SHSH blobs as soon as possible, especially if you're on a jailbreakable firmware like iOS 8.1.2.
We'll have more details in the days ahead. Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.