Mystery of Measure solved.

Last week I had some time to play around with the Measure example some more while I was staffing the stand at the ARM Developers' Conference.

I didn't see you there. Where were you? :-)

I also had a chat with my esteemed colleague Mr. Keil, who told me that there are a set of options in (funnily enough) the "Options for target" dialog called "Restore Debug Session Settings." These allow you to save breakpoints, watchpoints, memory and the toolbox settings between debug sessions. This means that if you set the toolbox option in that dialog (and it is set by default), you only have to define your buttons once and they are stored along with the rest of your project settings. They also override any attempts to define other buttons, which is why I was seeing what I was seeing.

Mystery solved!