This tool is a small adaptation of @samr7's vanitygen in order to generate Wispr vanity addresses.
For more information about it, check the accompanying README.
Use the "W" argument followed by the intended vanity address:

$ ./vanitygen -W Wispr
Difficulty: 4553521
Pattern: Wispr
Address: WisprXnaawMMSvzDB8YQTK8TjpnW2Nzzye
Privkey: 5sHWeeLpATNQ4LwqNmRGv9NFmeyeT6Lt1ejivNNe8uJmdsAkerm

Build instructions are supplied in INSTALL, and makefiles for Windows and Linux-based systems are supplied.
All credits go to the original author for developing such a usefull and powerfull tool.