Using calorific values of local takeaway restaurant meals...

Unless they publish them publicly, you can't just guess without potentially exposing yourself. With that you will need to keep on top of it as dishes and recipes change over time.

Yeah. Good point Leo.

I guess I could state clearly that it's an estimated figure perhaps? Not sure if that'd work though.

I'm glad someone pointed this out to me before I fired up emacs and began writing code ...

Does anyone else have any ideas for a health and fit_ness app that might be useful ?
 

If I was using an App like this I'd get the calorific values then use my Fitbit or Apple Watch or other Smart Watch to monitor my calorie burn.
I suspect most those in your target market already use a tool to monitor calorie burn and exercise level. Why would they use a second tool?

In short if the calorific value is an estimate then why not just do a google search for "how many calories in a Doner Kebab" and then use your FitBit to burn it off? Every existing device allows all exercise methods to be monitored and measured.
It sounds like reinventing the wheel (or reinventing the spare wheel).