Better explanation of heartbeat notifications

[harlo]

Currently, users may only learn of deactivation or crash via heartbeat notifications. In testing, however, our group didn't quite understand the use case; I would recommend highlighting this feature and why it comes in handy in the wizard.

[deviantollam]

i will say that the first time i got an SMS of just the heart emoji i wasn't realizing it was the heartbeat. i know that sounds silly, but it still might benefit users to see a small message or explanatory text on the configuration screen that "a simple single-character emoji heart will be sent"

this will also help if someone is using a device or system for monitoring that, for whatever reason, doesn't display the emoji Unicode. they'll just wonder why their device is sending them [X] blank characters, heh

[n8fr8]

Perhaps the first heartbeat of a session could include an explanation message "Heartbeat activate: You will receive a short notification ever X minutes while Haven is still running"

We can also include a setting that uses <3 instead of Unicode, or allows people to configure the character entirely

[lukeswitz]

• User configurable message w/explanatory text to initial message, as @deviantollam and @n8fr8 suggested
• Appended device battery percentage to the alert

Concatenating strings for translation purposes downstream. Feedback very much welcome, PR on the way. Thanks!