(Wow, third in a tight series of accurately predicting the future...)
Alembic has just built a prototype run of active guitar cables. 'Looks impressive.
I published my version of the active cable here over eight years ago:
I still use this a lot today, and I still think it'd make a great product. I don't know what specific technology Alembic is using for theirs, but it's very cool to see this and I'm sure they did a great job.
The Alembic cable looks even more like my very original prototype Preamp Cable... Lessee, I have it around here somewhere...
Okay, 'found it. Here's a picture of my original prototype, built, oh I dunno, around 1994 or thereabouts.
The guts of the FET Preamp are inside the plug on the right. It's phantom powered. The little aluminum box contains a 9V battery, and the phantom power circuit. There's a power switch on the side. The output goes to that phone plug epoxied in place, so you can just hang this off a guitar amp input jack. The jack on the side is a second parallel output for a tuner.
(It turns out that this particular package wasn't very good as some guitar amps don't have the physical space for a box dangling off the input jack. I was using this with a Fender Twin Reverb at the time, and that's got a sloping panel. My current Mesa/Boogie Lonestar Special wouldn't work with this at all. And the extra connection to the tuner is sloppy at best. So I dropped this packaging scheme early on and went with the "MXR Box" style approach.)