The bigger threat to Garmin is probably just the new GPS. There are probably a lot of folks who will now put off buying their first bike computer for a couple years now that an iPhone with Strava is going to be almost as accurate as an Edge 530 or whatever. Having a real bike computer is still going to be better, but by significantly less than it was a year ago.
One doesn't need to buy an expensive Garmin model. I've got an Edge 130 and an older Edge 25 that I've bought second hand. The 130 came as an upgrade to the older device and is perfect for my use. Both devices connect with my Forerunner 245 watch for the HR. Whenever I don't want to use them (commute or sub 20 km workout), I just use the watch. Dual frequency GPS is probably going to make its way into cheaper Garmin models soon enough, maybe thanks to Apple.
Having a phone on the handlebar/top tube is cumbersome and annoying, battery life is crap and distractions galore. I don't want needless phone calls from annoying people interrupting my workout and distracting me from watching the road. I've set up my Garmin devices to ignore phone calls and texts from the phone during workouts.
I've set up my Garmin devices to ignore phone calls and texts from the phone during workouts.
As an FYI, if you have an iPhone, you can set a "Fitness" focus mode that turns on automatically when a workout is started. From there, you can specify which contacts can pop a notification during workouts (or none at all). I let my wife and my parents get through.
But, like you, not that I'd use a phone as a bike computer to begin with.
As an enthusiast cyclist I don't think they is a threat to Garmin and Wahoo. The customers for those are enthusiasts who ride in all conditions and want a rugged device, a device with good battery life, a slim form factor that doesn't look off place on handlebars. Bike computers offer all of those, while phones do it only in a limited way. That has been driving cyclists to use bike computers for years, and not the lack of GPS precision. So I think nothing will change.
More casual cyclists might use their phones since they already have those and don't want to buy an extra bike computer - but that was already true in the past.
Some cyclists do already use iPhones with the Strava app as bike computers but they don't work very well. The third-party mounts are kind of janky, battery life is terrible, screen visibility is poor in some lighting conditions, and they don't support the ANT+ industry standard for common sensors such as power meters. An iPhone is adequate for casual use, but Garmin isn't really trying to target that market anyway. Those casual cyclists don't care about recording precise GPS tracks.
The latest high-end Garmin devices do support multi-frequency GPS just as accurate as the iPhone 14. Those chips aren't included in Garmin's mid-range products like Edge 5XX/8XX series bike computers but will probably be added in the next refresh.
