John_V 

As you mentioned, none of the head units (that I know of) will work with a WiFi connection that requires you to accept carrier terms and conditions of use. So a hot spot will be what you will need in order to upload your ride to Strava or other sites when away from your home network. But there's a big problem with this if you want to upload rides directly from the device. If you have your phone with you, downloading routes or upgrading the firmware isn't an issue and there is no need to use your phone's hot spot network, at least not with a Wahoo product.

The problem: when you set up your device for WiFi, you need a companion app in order to select the network's SSID (Network Name) and to enter the passphrase (password) to gain access to the network. This information is stored within the device and allows you to perform route downloads and firmware upgrades without the need for the companion app to be connected. So, unless the SSID and passphrase on your phone's hot spot network match that of your home network, your device has no way of connecting to the phone via WiFi. Since a phone can't connect to it's own hot spot, you can't use the companion app to change the SSID and passphrase within the device.

I found this out the hard way when a friend and I did a charity ride together, a year to two ago. We went to the ride in his truck and in haste, I left my phone in my van at his house. I thought I had downloaded the route for the charity ride but when I got to the ride, I found out that I didn't. I tried downloading the ride using his hot spot but the connection failed on each attempt. It took me a while before it hit me and as soon as I changed the SSID and passphrase on his phone, I was able to connect with no problem.