WifiSMS filled a major void Apple had five years ago. There was no way to send a text message from your computer. So way back on iOS 4, I wrote WifiSMS to do what the messages app does today, send and sync messages between your phone and your computer.
Jeff Benjamin from iDownloadBlog, made a great video explaining the functionality
I was very surprised to find out that this app had an unexpected user base, particularly iphone users with special needs. Here's an article and video by iclarified that explains how users with muscular distrophy were jailbreaking to install WifiSMS :-)