I've been asking about counting calories on another thread (some of you have kindly responded there too). The topic of HRMs has come up there as well. Thinking about what people have said there - and here - I'm in two minds now whether they're useful for my purposes or not. I think I need to read more and decide for myself. I'm pretty good at estimating my effort as I used to do a lot of running at one point.

For the type of rides I plan on doing, my iPhone 5S battery should be fine. But I appreciate the need to be aware of battery issues etc. I will be keeping that in mind when I ride outside. As I said, I can always get a bike computer later.