So much to do. No silly preambles this week. This week's long and rambly clue is brought to you by the letter Zzzzzzzzzz. (No, really, it's worth it. Read on!)
After California inventor Harry Chamberlin had developed and marketed his own line of electro-mechanical devices for a number of decades, one of his employees apparently took his designs to Great Britain in 1962, and struck a deal with a company to create a similar product (It's uncertain how much this was a sanctioned attempt to find a manufacturer who could execute an improved design, and how much it was a somewhat shady attempt to set up a competing product; in any event, later the two companies would reach an agreement by which restitution for the British versions's sales was made to Mr. Chamberlin).
The resulting device manufactured in Birmingham, England, was sold under a brand name that became moderately well-known within certain circles. The tempermental machines cost thousands of dollars, but nevertheless proved popular, and the most influential version -- the M400 -- sold over 1800 units after its release in 1970. It's novel characteristics were instantly appealing to many, and a number of celebrities, including Princess Margaret, Peter Sellers, King Hussein of Jordan and L. Ron Hubbard, were among the purchasers.
However, in reality these were usually purchased by commercial outfits and used only by professionals and for limited duration. Although they were not originally intended to be portable, there was increasing demand for the devices to be capable of moving from location to location, and the M400 and subsequent models were frequent used in this fashion.
Interestingly, one of the people who had worked at the Birmingham factory where it was developed, Michael Pinder, later got ahold of one of the devices and put it famously to use in 1967.
By what commercial name was this invention known when it came into use?
First correct answer posted to comments gets a virtually unused set of children's rainboots, size 7, in periwinkle. No Googling or using the abbreviation, "T.M.I." By that I mean: please don't use that abbreviation anymore. Let's just put it to rest. One guess per comment, but comment as often as you like.