Sympathetic vibration is the best kind of sustain you can get, but it's not always easy to achieve on-demand, which is why there are devices like the Fernandez or Sunstainiac. Ebow, at least back in the day, took a few moments to 'kick in', which was actually part of its appeal, but limited its usability for certain applications.
On Project Guitar, there's a 70-page thread (or so, I'm just guessing, but it IS super-huge) dedicated to homebrewed 'sustainer' systems.
Note that unless you have a 'device', you won't get sympathetic feedback by tracking your guitar with headphones on.
Greg


