It's an interesting domain to think about. The big one would be re-establishing communication networks, being able to coordinate with groups across a large area is obviously the first thing any group with power (or looking to establish power) will do after ensuring food, water and shelter. It's pretty much a necessity if you want to maintain any power.

I could see embedded style sensors and technology being very practical, tools for measuring temperature/humidity etc and logging it constantly, sensors to measure water levels in rain tanks, basic inventory systems for food, basic automations for things like farming (automatic watering systems/collection systems even?)

Security is another one to think of: Sensors to detect people entering/leaving an area, trail cams for hunting, alarms etc.