I'm not sure why your phone battery runs down. I have an 810 and use Garmin Connect on my phone. Garmin Connect allows livetracking from your phone but it doesn't use the phone GPS. Recently I got about 8hrs out of a Livetrack with still plenty of life left in the battery of the Garmin and phone. Plus if required you coulod use a power bank to charge both on the go if reqd. Garmin Connect allows you to send a livetrack by email or other and the track can remain active for 24hrs if reqd.
I've also tried Glympse and it works well too but it does use more from my phone.
When I've used the Strava app on my iPhone, obviously using GPS, the battery has drained within 4 hours. I presumed Live Tracking would be using the GPS on my phone either instead of or as well the GPS on my Garmin. If that's not the case how does it provide the data?
The other point to keep in mind is I have chosen to have a very small data allowance on my iPhone. I only pay £1/week for 25 minutes calls, 50 texts and 60MB of data. The calls and texts are more than adequate for my weekly needs. While I worked my employer was paying for a huge amount of data which I was able to take advantage of, now I'm retired I've chosen not to pay for a lot of data just to have the convenience of accessing the web while I'm out of the house. To date I haven't found this to be an issue but I might change in the future - currently I don't feel it's necessary but a luxury.
I do like the idea of the stand alone devices being suggested. Spare batteries are easy to carry and one never knows when I phone might fail through battery, physical damage or lack of signal. While I shall value the safety aspect the BIG issue is convincing my wife I will be safe, she can check this reliably and be convinced I can carry on solo touring!! Either that or I have to find a touring buddy.