I have the SyncMe app, and I would like to have a widget activating a fuction in the app.
Now I have to open the app -> Click on a button -> Click on another button.
Can I have a widget doing this by just clicking it?
In short, you can't.
Only the application can interact with itself internally, unless an API was created for that end. External applications aren't able to know what to do in order to follow your desired "path".
The best you could achieve is opening the application, but you still needed to manually tap the buttons.
I believe you are trying to have some sort of "Sync Now" functionality without having to open the application and clicking some buttons to achieve that. Either case, Email the developer and request such widget, I'm sure it's useful enough and interest will arise.
Working on it, you will have a shortcut in the next release of Syncme. Not a widget, gone through all the source code of the Android music app widget to figure out that will be an overkill :)