Right
The thing called Roland GK-3 (or an older version GK-2a). Alternatively check some solutions from Graphtech.
Alone this thing won't give you any MIDI signal, it must be paired with Guitar Synth or converter (like Roland GI-20). However the result is not that perfect. I had such a device. As long as you use sounds from Guitar Synth it's ok. But if you try to use it as a MIDI controller for an external device it brings a lot of problems. For example Roland GR-20 splits MIDI signal into 6 channels, each for every string to be able to use pitch bend for each string separately. If you use another option and combine singnal into 1 MIDI channel it's hard to play tight and clean since the pickup can't react on your playing smooth enough.
I had such a device for years and used it live just once. Recently i bought KB37 keyboard from Line6 and use it on stage. It can process guitar signal and you can use it as a sound card and MIDI controller at the same time. Both guitar and synth sounds from one device.
