Havnt seen one Colin, any link to photo or sales pitch.
All is needed is movement of air across the carpet or furniture. There maybe technology in it, but the cost of snails and downdrafts seems a lot of money to pay (£160-£300) when you can get someting that is effective for £30-£40.
I have had a downdraught and a snail, yes they assisted in the drying, but most of the time just took up bulky space in the van, hence I sold them just over 12 months ago. Richard B-F was selling one couple weeks ago for the same reason I think.