I think all of them use the same service for SOS calls. I’m not sure if the Garmin, Zoleo, or Somewear subscriptions include rescue insurance.
You deactivate your account using the Bivy iPhone app underStick>Account settings. You’re allowed a single preset message–the inReach allows you three distinct presets. This is set up with the iPhone app when you’re in wi-fi or cell data range. I’ve successfully changed my preset when in the backcountry.
I think there’s a corresponding Android app.
As for tracking, the others have some sort of charge for tracking, depending on which data plan you’ve signed up for.
The best device for you depends on how you’ll be using it. Adventure Alan reviewed some of them (but not the Bivy) here:
https://www.adventurealan.com/best-satellite-messenger-inreach-vs-spot/
and rightly noted that the cost of data plan over a few years was more important the price of the device.
So how am I using the Bivy? I have GaiaGPS to record tracks and drop waypoints if I want to refer to my hike after I get home. I use GPSdiagnostic to (1) check if I’m getting a good GPS signal if GaiaGPS is acting up, and (2) send texts with my location if I’m in cell range. Weather forecasts I can get before my trip–they’re pretty accurate for a 3-day horizon.
I use the Bivy for check-ins every few hours when hiking on trail and every 40 minutes or so when venturing off-trail. I do two check-ins at the same place when I make camp at the end of the day, or reach my truck at the end of the hike. I’d use the custom messages only when something eventful happens or if I have a build-up of message credits from the monthly rollovers.
So the minimal Bivy plan works for me. YMMV.
BTW, Bivy’s pricing is a total cost. There’s a line for sales tax on the invoice, so Bivy might collect sales tax in Utah. I think Garmin tacks on those pesky fees that you see on your phone bill.
Some more comparisons are here:
https://www.outdoorgearlab.com/reviews/camping-and-hiking/personal-locator-beacon/bivystick-blue