The cool thing about a cell phone are sensors; the more the better and unfortunately the more expensive.
I live in the countryside and use apps like dipping compass, compass with camera, humidity, barometer (atmospheric pressure), magnetic field, level (plume), noise meter (cicadas and birds singing), solar incidence on plants (lumens), ... .
I photograph plants and insert information from planting, germination to the time of the fruit and automatically add it to the agenda. To perform work in the field is a good utility, I listen radio when I am in the field, a wireless headset is good.
Something I noticed in chickens is that the grunts mean messages; there are grunts to find food, another to hide, another not to get close I'm angry, another to please don't get close, .... Interesting.