No, not heard of them. All I would say, is to be careful of anyone or any company who asks you for personal information including your address etc, bank account details, online account details, or asks you to send money to receive certain benefits from them.
Like you said, they contacted you and not the other way around, so be careful. Saying all that, it could be genuine BUT it's your call.
I know this thread is old, but I was wondering if any of you have had the chance to try the written.io service yet? I got an email from them today letting me know that one of their brand customers is interested in licensing a blog post from 3 years ago.