So I now have 3 prototype board assembled (photo below) - 2x CC2541 and 1x CC2540. I can now use these for experimenting and software testing (I need to build some sort of automated test runner ... but more on that another day).

In the meantime I'm struggling with the question of power. The BLE module does best when powered near 2v (due to internal voltage regulation, powering it higher than that is just wasting watts). Realistically, nothing external is going to run that low, and would much prefer 3.3v. So what kind of power supply should I put on the board? If I assume a 3v supply (a coin battery or maybe a couple of AAs) I could boost that to 3.3v but will also have to buck it down to 2v. I don't want to have two power systems :-( Alternatively, I could just run the whole thing at 3.3v (boosted) but that's wasting energy. Another options is to run the BLE module directly from the battery, and just use to boost for external stuff.

At the moment, no ideal solution springs to mind. Still thinking ...