Regarding smartphone apps, you don't need to give up privacy to benefit from some useful apps.
And I'd strongly encourage anyone to carry a phone for emergencies. You don't need a voice/data plan to dial 911 in the US. However a voice/data plan enhances our ability to make calls, including 911. Some phones can carry two SIMs, and Google's Fi phone service can access multiple networks in the US and some other countries.
For the most privacy, just buy a cheap Android phone and don't activate it. Just use your home wifi. Download Wahoo Fitness. It's free, works well, and stores data only on your own phone. You can transfer activity data to Strava (which I do) or other apps but it's not necessary. And to be sure it's not transferring data without your permission, disable wifi after installing the app. It'll still work with GPS.
I used this method with an older iPhone 4s a friend gave me after he upgraded. I didn't activate the iPhone for the first couple of years. Just used it as a GPS device for cycling apps and navigation maps. It was usable for emergency calls via 911, but doesn't need a voice/data plan for that.
I also used Cyclemeter for iPhone for a year, the paid version (only $10 a year). By default it stores our activity data only on our phones, not to the app company servers or our own cloud storage unless we chose to. However Cyclemeter didn't do much that I wasn't already doing with Wahoo Fitness and Strava.
There were a few advantages to Cyclemeter (besides being reasonably private by default):
- User customizable workouts with voice prompts. Very handy for folks who don't want or need to look at their phones. I found this handy.
- Records weather data (and can share it to Strava or other apps/sites, if the user chooses). Also handy, to keep track of tailwind assists, headwind hindrances, or neutral wind conditions.
- Versatile user customization options, but not too complicated to figure out. I didn't use most of those features.
Another advantage to Strava is access to Strava-compatible apps for making better use of our ride data. For example, the Elevate app can be authorized to use our Strava logs and give us useful info about our performance and progress in various categories. I'm pretty fast on downhills by any standard, even at my age (61) and only moderately good condition. Just a consequence of being naturally aero -- skinny with fairly narrow shoulders, but weighing just enough to have good momentum, being able to spin up to 130 rpm in whatever my biggest gear is, and not being nervous about speed. But I'm a mediocre climber. Always have been. So I'm more interested in how I'm progressing with the tougher stuff. Elevate helps make sense of Strava logs in useful ways, so it's not just my subjective impressions.
There's another app (currently not being developed, I think), that factored in wind. Big help for distinguishing between my best times wind a tailwind assist compared with neutral wind or headwind on the same segment, direction. I find that very helpful because it's realistic. I have a few top 10s on some tough segments, alongside some very strong local riders including some pros. But the wind factor app makes it clear that I was benefiting greatly from tailwinds, while the other riders had less tailwind or even some headwind or quartering wind.
These apps remove subjectivity, fantasies and clarify where my strengths and weaknesses are, where I'm making progress or regressing. That's more helpful to me than average speeds, power estimates and data that doesn't include real world conditions. It shows that over distance and a range of terrain and conditions, I'm just a very average cyclist and not even particularly strong among 60+ year olds. That's a good thing to know because it motivates me to train with realistic expectations rather than be fooled by appearing to be "as fast as so-and-so" when in reality those other riders could drop me like a rock.
The only downside to Wahoo Fitness app is it shows minimal info via the app. It records a lot of data but doesn't show it. We need to transfer the data to another app or site to access the data. I use Strava as another social network for keeping up with friends so I transfer my activity data from Wahoo Fitness to Strava. But I still choose which activities to share and which to keep private (well, just between me, NSA, Google, Strava, and a few hundred Russian and Chinese hackers... but private by 21st century standards).
Another reason to carry an activated smartphone for emergencies is to have a silent objective witness. By giving Google Maps Timeline permission to record all of our activities by default, it's always on. No need to remember to start it. It's remarkably accurate at guesstimating our mode of travel, whether bike, walking, running, private vehicle or public transportation. This was critical last year when I was hit by a car -- it confirmed my version of the location and incident, time, etc. And it automagically records my many medical appointments, so I don't need to keep a separate journal (although I do for personal notes including subjective impressions of how I'm feeling, pain level, etc).
It's private by default, although we could choose to share it. I don't. Google data cannot be edited, altered or falsified by the user. It can only be deleted (although Google probably keeps it indefinitely anyway). It can be downloaded and converted to another data format for use with our own databases, or apps like Strava. Those can be edited or modified. But not the original file. Also potentially handy for legal purposes, although I don't know whether it's been done yet.