Funny, I'd just been Googling Konnyaku, which is another name for Konjak. It's got lots of other names too, depending on the country and use. I've heard of Shirataki noodles and that's another name.
I spotted it in a Groupon email at the weekend in an offer to buy multi packs from the Better than range. I'd never heard of it before and it was the nutritional value that made me interested because basically it doesn't have any.
It's been around for hundreds of years in Japan and in parts of China and takes on the flavour of the other ingredients in your recipe. The flour used is starch resistant and not absorbed in the same way as regular carbs. The jelly is used as an alternative to gelatin by vegans. It's sold in water in plastic bags for many purposes, including as a diet product. It looks like the company that makes the Better than range has simply made it look like pasta, rice and noodles, so it can be sold in the West as a healthy product for weight loss.
Looking on Amazon and checking on the Diabetes UK forum, there's three brands that are popular in the UK - Better than, Eat Water Slim and Bare Naked (the most popular). Some people don't like the texture and others say they have a funny taste, although that seems to be down to not rinsing the product well enough when you take it out of the packet. The big downside is the price - it's expensive, which is presumably why it was in my Groupon offers.
The Amazon price does vary quite a bit and you do get a lot in one packet, so I might order one the next time I buy something from Amazon as a way of reaching the free P&P amount. If anyone else tries them, do let us know. Apparently it's popular with Weight Watchers followers, so if you know anyone doing WW, please ask them about it. It could make life for us veggies easier. 