If you are just going to sail in the US West coast
area,the SPOT is adequate and your cheapest bet. SPOT however does not have any way to send messages but very short pre-written messages prior to departure. The manual I´m OK messaging is free and the Tracking every 10 min cost around $50.- per year.
However,if later you are extending your cruising areas world-wide I would definately
recommend getting the initially more expensive inReach by Delorme whixh uses Iridium
world-cover satellites and also has the capability of short two-way messaging.
The in Reach cost around $ 250.- and unlimited tracking $ 25.- per month which also includes a set number of massages per month with a supplement exceeding the limit.
inReach connects up with most smartphones,Android and iPhone
Both SPOT and inReach can also send their data to the FREE SpotWalla public page which can display your present position to family
and friends every 10 min.