I live in China and wechat is used for everything. It is the...

I live in China and wechat is used for everything. It is the method of choice for all age groups; it's used for business interaction, text messaging, calls, people use it to pay for taxis, the chinese version of Uber, paying bills in restaurants / cafes, transferring money between friends.....everything.
It is extremely hard to get a monthly payment plan for mobiles here and everything is pretty much pay as you go. A lot of people will top up their phone payments via wechat as well. Internet usage on phones / tablets is pricey here compared to Oz although the availability of Wifi is far better than my recent experience in Sydney over CNY.
Wechat is the best app available in China and there is little to no use of whatsap and certainly no facebook.
I have introduced friends and business associates outside of China to wechat and they love it. It could quite easily explode in other regions but as you say, the market in China is hardly small!
The potential for PSF in this part of the world is huge.