iH8sn0w is working on a tool that will dump your iDevice’s current SHSH blobs, even if they are unsigned from Apple (TinyUmbrella can only save signed blobs). This is handy, for example, if you buy a new iPhone running 4.1 and need to back-up the blobs. Since Apple no longer signs 4.1 blobs, they cannot be saved via TinyUmbrella or Cydia, but iH8sn0w’s SHSH extractor tool is able to dig deep down and preserve the blobs regardless.
@prasys working on this SHSH blob extractor. So if a new device comes with a firmware apple isn’t signing, you can dump it.
The tool will not allow users to save blobs after the device has been restored and updated, since blobs are completely wiped from the device. So, if you install a tweak on Cydia that happens to bork your shiny new 4.1 device, causing it to go into a boot loop, you have no other choice than to restore to the latest firmware. Under normal circumstances, you would loose your precious untethered jailbreak, but with the blobs saved, you will be able to use your saved 4.1 blobs to jailbreak with the upcoming redsn0w.