After 3.5 years ... :)
My team at Ramen recently highlighted some of the internal features in a standalone product that does just that: https://ChartURL.com
You can create diagrams "on the fly" using the "Encrypted URL" scheme, or you can send us a huge amount of data and return a short URL that will be allowed for the image.
It was built on top of C3js.org, so there is a subtlety of flexibility in what you can create.
These URLs can be used in web and mobile applications, but the original intentions were email addresses, so I hope this helps!
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