@szczymEye-Fi don't run stable for a longer time, the camera must be restarted (manually) from time to time (it was reported at least after some hundred images)...
Are you sure with gphoto ? I thought it should work...
Another possibility:
the SDM (Stereo Data Maker, a CHDK fork) can switch between playback and record mode from a running script, it should be possible to transfer the images automatically when the camera comes to playback mode; in playback mode images normally can be transfered via PTP (Picture Transfer Protocol).
You can have a look to the
SDM homepage, especially to
Image uploading,
Uploading to the PC at regular intervals and also to
Continuous immediate uploading to the PC.
The first two links points to a Windows solution (WIA-Loader, a Windows .NET app) - but the WIA loader is widely MONO compatibel, maybe you'll get it to work under Linux (or Wine).
The third link points to a solution using the commercial application "PSRemote", also a Windows application, but maybe this will run under Wine...
But first i'll give gphoto a 2nd chance, maybe you'll find a solution, it's a pretty nice & powerful framework...good luck !