Text messaging service for older devices [iPhone 3G]?

Hi everyone,

I got an old iPhone 3G which I gave to my mum and I have been busy looking for a Text Push service, like Whatsapp which is not available anymore on iOS 4.3-previous devices, for sending messages over the internet.

I tried to make Whatsapp working, jailbreaking and changing the CFBundleVersion, as suggested on some forums, but with no luck.

Is there anybody who knows an text messaging app? I have an iPhone 4 so it doesn't have to be necessarily cross-platform.
A few years ago I knew a service called pushme.to but it looks like it has been shut down.

Any help appreciated!