Does it work without signal?
Yes. The crew app keeps your jobs on the phone, and clocking, parts, notes, photos and finishing a job send when the signal is back.
Yes. Each job is saved on the phone whenever it is opened with signal. With no signal the crew still see their jobs, even when they open the app with none, and clocking on and off, adding a part, a note or a photo and finishing a job are kept on the phone with the time they were pressed. They send by themselves, in order, when the phone is back online.
A few things need signal, such as signing in, opening a job for the first time, a job's other files and the assistant. See Working without signal.