Qt Update project - Opinions wanted

Hello,

I'm working on a project and I need your opinion. I'm currently designing an application that updates another program and downloads files from a server. It is an update tool for a media application. There are a few requirements:

1. The application must run as a daemon/service.
2. The transfer must be secured and each client must have it's own update folder on the server for the data files of the other application to update.
3. The application must be able to update an externel app.
4. The application must be able to update itself when a new update is available.
5. The application must be able to detect and write to a removable hard disk drive.

I think 1. could be done with QtService from Qt Solutions.
FTP is out of the question because FTP is not secure, setting up SSH accounts for each client is too time consuming. What is the best option in this case? HTTPS?

Another problem is updating the application. How to know when a new version should be downloaded and installed and how should the application update itself? Maybe an external update tool?

The external application: how do I keep track of the updates and how should the external application be updated?

The removable harddisk: How do I detect it's plugged in? ( RegisterDeviceNotification and Qt event handler?)

These questions already have an answer by me but is this the best solution? I doubt it, I hope you can come up with better ones instead.

Thanks for taking the time to read my post :)

pvdk