What is different to the EBow and other Sustainers?

You can use both hands for normal playing. Feedback is created by positioning the guitar neck to the Resonator. This is similar to the speaker positioning for regular guitar to amplifier feedback techniques. However, the onset of feedback and harmonics can be controlled much better by the Resonator positioning. This feature alone is one of the main differences to that of built-in Sustainers. Plus, unlike the EBow you can get feedback with more than one string!
Electric guitars can be used without any modification. You do not need a special guitar nor any additions to your beloved guitar. Guitar Resonators are just added to the equipment you are familiar with.
All Guitar Resonators have an external power supply, whereby the magnetic field is much stronger than battery powered devices. This gives you the ability to get feedback with very high or low strings too.
Built in Sustainers are connected to the bridge pickup, whereas the Resonator is driven by the selected pickup(s). Feedback playing with different pickups offers many different feedback sounds. This feature is similar to real amplifier/speaker feedback.