Now it is put on sales at the Japanese Ricoh online store (Google English translation of the page Here).
It is learnt that Serial Number of the camera shall be provided for the purchase of the license key for unlocking the function. The key is not portable across different bodies and one key is solely for one unique camera body. Besides, it should be noted that product keys for the K-1 and K-1 II are different. The price of the product key (without tax) is in Japanese Yens 10k.
Upon purchase of the key, Ricoh will send the buyer a QR code which the camera will read the code to unlock the function. It says it takes from several days to one week for Ricoh to generate and send back the code to the buyer. It seems that everything is being processed manually. The worst thing is that if the consumer has entered the wrong serial number of his/her camera, Ricoh will not be responsible for it and the correct code will not be resent?! :-|
As for the operation of the function, read the Chinese article here. The working principle is also briefed in the article.
In short, the camera takes two consecutive photos according to the maximum Exposure Value (EV) difference. The camera will then process the photos and clone them into one with the selected gradual ND pattern. And, the pattern of dark/bright sections could be set by the user. It is recommended that the user should put the camera on tripod when using this function.
The EV range could be from 0.3EV to 5EV. Some example results are as below:
