I need to write a windows program that
1) sends a .sis file to a Nokia 9300/9500,
2) installs the app (with minimal device user interaction),
3) runs the app, and
4) then communicates with the app (ideally, such communication is written above the transport layer, i.e. through an mRouter API or Nokia Connection Manager API).
I want to do this on the Nokia 9300/9500, which doesn't use mRouter, so I can't use any mRouter APIs or the Symbian Connect QI SDK built on top of that.
With OBEX (OBject EXchange) you can send the installation package to the phone (over, e.g., Bluetooth or infrared). However, you have no control over what happens on the phone side.
On the phone, if you haven't written your own app and installed it in advance on the phone to handle the incoming .sis file, it will end up in the phone's messaging Inbox. From the Inbox a user has to open the message and install it manually.
If you work for a Nokia Forum PRO member company, from the PRO web site (http://pro.forum.nokia.com/) you can download the Nokia PC Suite API with which you can install an application on a Nokia PC Suite supported phone (in other words, do what the PC Suite Application Installer does). It depends on PC Suite being installed and working on the PC.
Even if with PC Suite Application Installer or your app that uses the API, the installation will be launched on the phone, but the user has to manually finish the installation.
Digression: The Symbian OS does not allow silent installations of software on the device. That is a good thing, because no malicious software can be installed secretely (without the phone user seeing it). The user may still not realize it is malicious software, and installs it anyway, but then it is never wise to install any software on any device which origin and purpose you don't know (especially if it unsolicited and/or sent by total strangers).
Back on track: How your phone app communications with your PC app after you've gotten them both up and running depends on the connectivity and APIs. The crude way would be OBEX file transfer, PC Suite file transfer APIs, other means over Bluetooth, etc. (see, e.g., Bemused as an example app to do it in one way: http://bemused.sourceforge.net/).