When you need assistance
This is where things start to get a bit blurry with more options. A “help me now” type of beacon is not appropriate here. All you need is some assistance – a tow, help digging the car out of a bog hole, another spare tyre, a bit of fuel, etc. You’ll probably have enough food and water for a few days and be in pretty good health. Certainly not life threatening in the short term – you’ll be OK for a few days to a week or so. If you discount radio, which I’ll go into in detail in another post, you’re basically left with mobile phone, satellite phone or something like the Spot Gen3. At a stretch you could even just wait until someone else comes along. You need assistance, not an urgent rescue.
You probably won’t have mobile phone coverage and for most people HF radio is not in the equation. That leaves satellite phone. These things are expensive and so are the plans but there is a cheaper option. Hire the sat. phone for the duration of the trip with a plan that only sees you paying for calls and messages. A quick search will uncover a heap of companies eager to garner your custom.
Another option, which is far from cheap, is a sleeve for your smart phone which effectively turns your normal smart phone into a satellite phone. Read about them here.