That's one thing to remember about SPOT, unlike the COSPAR satellites used by PLBs (or even some other satphone systems) the satellite must have both you and a ground station in view at the same time.

This means it doesn't work in the middle of the ocean, a lot of Africa and in a few countries with uncooperative telecoms providers.

There is also an issue of who they are going to call even if there is a link. Does SPOT have a relationship with or even any contact numbers for the Yemeni coastguard/army/rescue ?