I've been reading the brilliant Triathlon Training Book by James Beckinsale. James recommends regularly tracking your performance profile - strengths and weaknesses - using a radar chart. I couldn't find something out there that was exactly what wanted (and I don't need much of an excuse to code). So, this is the result.
Move the sliders to set your current performance levels and click Save to generate a bookmark with a 5-letter code. Keep this bookmark - it refers to your data. Revisit this site, using your bookmark, and update and save your performance levels as you improve. Once you have a couple of saves, you can click Play and watch your progress.
I've since found out that James offers a tracker spreadsheet for free if you sign up to his newsletter (see: http://www.jamesbeckinsale.co.uk/performance-profiling/).
Warning: myjson.com is in beta - it seems pretty reliable to me but, if you want, you can backup your data by visiting http://myjson.com/<bookmark> where <bookmark> is your 5-letter code.