Hello Raul, Rebecca and Chris,
Firstly, I agree with Raul, I am not aware that it is possible to send
somebody an iOS app as any iOS app paid or free is tied to the specific
Apple Id which was used to download it. If this was not the case, everybody
and their dog would give all their friends the apps they purchased.
Anyhow, a quick google search for "Syrinx" says that Syrinx is a "native
Twitter client for OSX". I assume it is similar to what Qwitter is for
Windows and since I am not a Mac user I have no idea if Mac apps can be sent
to other people.