It features customizable current curves and many other customizations all on the fly.
Unlike regular CFW which is based on Ninebot firmware files with bytecode patches applied, SHFW is compiled directly from C source.
At this time it is closed source and there are no plans to open source it.
At this time SHFW can only be installed through ScooterHacking Utility (SHU) on android.
Any other apps for Windows, Mac or iOS promising the ability to install SHFW are likely scams.