Not sure what you mean by not mainstream :P, but here are some artisanal APIs that I like and have found on the Mashape market place (https://market.mashape.com

Not sure what you mean by not mainstream :P, but here are some artisanal APIs that I like and have found on the Mashape market place (https://market.mashape.com/explore?query= https://market.mashape.com/explore?query=). - mSend, send SMS, https://market.mashape.com/webaroo/msend https://market.mashape.com/webaroo/msend - Have I been pwned?, https://market.mashape.com/troyhunt/have-i-been-pwned https://market.mashape.com/troyhunt/have-i-been-pwned - (inofficial) Whatsapp API, https://market.mashape.com/datayuge/whatsapp https://market.mashape.com/datayuge/whatsapp