Signal allows you to explicitly open the app, get your current location, and send that snapshot of your location to someone immediately. That's definitely fine for some use cases.
Zood Location lets you share your location with other people without having to do anything on your part (besides accepting the initial friendship). Then your friend can simply open Zood Location on their phone and they'll be able to see where you are and you won't have to do anything. It's very useful for families trying to coordinate dinner plans after work, determining how soon your partner might be back home to help with the kids and other seemingly trivial things that usually require multiple disruptive calls and text messages.