Help Me -> Create Sis File

No code, but I think there was a ready-made app for older S60 phones that could build a .sis on the fly (and send it to some other device). I don't remember the name of it or the app or its developer.

In any case, if you want to do something similar, look into the makesis source code and specs on http://www.symbian.com

Note that it'll be much harder with Symbian 9 based devices, as you have no access to other applications' private directories (only your own or unprotected directories), and you also have to sign the installation package.