I saw several in the bigger cities in China when we were there this month - e.g. Shanghai and Beijing. That said, from what I've heard about Japan I don't think they are as prevalent in China.
I didn't see even one 'fancy' toilet in any other country we visited in Asia: Vietnam, Indonesia, Thailand, Cambodia, Burma, Sri Lanka, India, Nepal, Malaysia. We spent about a month in each and intermittently visited more expensive establishments so I guess we got a reasonable idea of what's around...
This general observation is also supported by the Wikipedia article I just checked:
The largest producer is Toto, with 65% of the market share, while the second largest is Inax at 25%. The main market for washlets is still in Japan, and TOTO reports that overseas sales account for just 5% of its revenue. The primary foreign market is China, where Toto sells over one million washlets each year.