Yes it is not 24/7 and is not realtime, but it is a free way to receive a message from family shoreside in case an issue arises.
Obviously everyone's case is unique. If I knew I would need to be contacted, I would leave my phone on and deal with roaming charges. But I always leave the Carnival emergency contact number with my house sitter just in case. Thankfully I have never received that tap on the shoulder while cruising, and prayerfully never will.