Have been a longtime user of WifiSMS, and really appreciate a regularly updated alternative. Just a few suggestions:
1) Could you make it clearer that Remote Messages is best used with a tweak that keeps the iPhone WLAN on. Provide links to the tweaks in the FAQ and the app description on Cydia. Otherwise new users will keep asking. I've found KeepAwake more reliable than Insomnia, so perhaps suggest both. http://planet-iphones.com/cydia/id/net.ispazio.keepawake
2) Could you provide an option (in settings on the iPhone) to change the font for the browser UI? Perhaps to something more Apple-like (e.g. the font from Apple Messages)?
3) It would be amazing if you could get someone to integrate this with Notification Center on Mac OS X (as Apple's Messages app is), even if it just makes FF send the notification.
4) Lots of people I know who aren't Jailbroken would probably be willing to JB just for this. Have you considered putting something in the FAQ explaining that you need to jailbreak, and providing a few links to JB instructions?
Anyway, sorry of the deluge of possibly unhelpful suggestions. I think this app needs more coverage! Should be up on modmyi, iphonedownload blog's youtube channel, macrumors, have you thought of posting/contacting them...?