Electric Bikes - Are there any pedal sensing chain driven kits?

The one thing I love about my Bionx is that the riding experience is still like a bicycle. I don't have to use a throttle to get the assist. It senses my pedalling effort and multiplies that. However, it still has the drawbacks inherent in hub motors - cogging effect (drag), weight, and efficiency.

Chain driven motors add no drag in the wheels, their motors are a few pounds lighter and smaller, and they can operate at peak efficiency at any speed my gears allow (that translates to longer range).

For my next e-bike, I'd like to find a chain driven kit that can also multiply my pedalling effort like Bionx. Does anyone know of such a kit that's out there?

That's what I love best about the Panasonic drive on my Giant. No twist throttle at all, it's all from the pedal sensor and it gives more the more I put to the pedal. And the fact it's a chain drive is cake too.

Other than Bionx I haven't seen a kit with a pedal sensor. Maybe if you can source just the sensor from Panasonic or Bionx and then use that as the throttle to a motor.

One thing about chain drives is you need quite long chainstays to have room to mount the motor between the seat tube and the rear wheel.

Hmm... we also have a Giant LaFree e-bike. It's about a couple of years old. Although the assist is pedal activated, it definitely does not vary according to my pedaling effort. I assume it also uses the Panasonic drive. If so, did they add a variable assist sensor based on pedaling effort?