Semi-Restore: Upcoming tool claims to let you restore the device to a fresh version of iOS without losing jailbreak

• 5-10 minutes of your time!
• A computer running Windows or Mac OS X
• OpenSSH and APT 0.7 Strict (NOT THE LIB) installed on your device
• An SSH client on your computer (USB version coming soon)

Semi-Restore website also highlights the following important points about the tool:

• There may be a better way to fix your current problem. For example, to fix “Safe Mode” issues, you can just uninstall Mobile Substrate from Cydia.
• Like any other restore, make sure you backup your data if you want it later.
• Avoid using your iOS device or anything related to iTunes or XCode. Why not actually go outside?
• This process can not and does not repair broken system files! Avoid all Siri Ports, as they are not only illegal (except for Spire on 5.0.1) but they also create problems and may potentially break system files (even Spire can cause this).
• Your device will respring several times during the semi-restore. This is perfectly normal, so don’t panic.

The developer has also released the following screenshot of the tool:
I was a little skeptical about it as I haven’t heard about the developer before. After some digging, it looks like the tool is simply a wrapper for iLEX R.A.T.