Create datafields without the SDK?

This is a suggestion for an app that provides users with the ability to create and deploy simple calculated data fields from say a browser interface.

This could take the form of an app a bit like FaceIt that deploys a Connect IQ app to devices, or it could be a part of Garmin Connect in the same way that simple data fields can be created on Suunto's Movescount.

I have seen that there is an excellent custom data field here which is related in concept. The DIY data field is focused on the rendering the data in existing data fields.

My proposal focuses on being able to specify a calculation of a value for the data using one or more data values and constants as input and rely on the app e.g. Running to render the data field just like with the built-in data fields or the many CIQ data fields that produce a single data value.

Examples of calculations are
Cadence / 2;
500 /((cadence) x (pace in minutes))