I feel like i had one in reaktor years ago, but wondering if anybodys seen anything recent?

 

I believe that the reaktor ensemble is the only/best attempt to emulate it. This is a personal opinion, but I believe that the magic of Swarmatron is mainly based on its interface. Replicating something similar functionaly in software like Max/MSP, PureData, VCV or even Vital isn't hard. The magic is in the ribbon and how you are able to interact with it using your hands.

 

I guess this device is no magic, actually pretty simple as seen in clip.
To replicate you just would need a schematic diagram (number of oscillators, waveforms, filters and the like), and a ribbon controller.
Then yes, with reaktor its replica would be feasible.

 

In eurorack there is a module that is out of production by synthesis technology called the e340 Cloud Generator. I bet you could get close if you got 2 or 3 of them and controlled them with a cv ribbon for pitch and a pitch bend wheel on a keyboard controller to control the spread.

Another cool way to deal with the pitch tracking and portamento would be with a midi guitar pickup. Using a CV pedal to control the spread.

Analogue Systems used to make a Ondes Martenot controller called the French Connection that would also allow some of the gliding style of the Swarmatron.