Syncing data between smartphone and pc

I want to create an app for android. In this app the user is able to collect data and save them to the local storage (maybe sqlite or as xml documents). Because the app is only for collecting data to go, the user can evaluate the collected things on the home pc using a desktop application. So for that, the user has to sync the data between android and the desktop pc. I found that a common way is to push the data to a cloud service and let the other application get this data on startup.

My problem is, i think my audience will not spread its data trough the internet so another solutions have to be found.

The best way i think is to sync this data via USB cable and if available via WLAN, a third possiblity could be, that the SD-Card is used as the sync medium. Therefore the Desktop-App has to detect this card and searching for a special folder or file on the sdcard.

It has to be easy as possible, when the desktop application is started and the smartphone is connected, a dialog should popped up and the user is asked to syncing data.

I read a bit about this theme and its oviously not trivial.

With this consideration iam also thinking about the data storage technology i should use. Should i use sqlite or xml for storing data? sqlite is easier to handle data and its easier to perform querys. xml is good for interchange data. syncing between pc and smartphone only means to copy xml documents on the file level. With sqlite i have to copy the whole database but i dont want that.

Whats your experience with this theme? Whats a common syncing architecture for doing this?