I have tried looking for WhatsApp on the App Store from within my iPod Touch but it did not find it.

After a quick look on the net, I learned that you cannot use WhatsApp on an iPod Touch. However, I have seen it being installed on a Jailbroken one - not sure if one can simply put the *.ipa file to the Touch so I can use WhatsApp without having to jailbreak my iPod...