Another way to go is a rugged phone.

This is my bike computer.

https://www.amazon.com/RugGear-RG710...=ruggear&psc=1

It's not a great cell phone because its' 3G tops, if 3G hasn't been shut down in your area. But Wifi works fine so you can load everything you need at home. GPS works fine.

And its battle proof. Fully water proof. Mud proof. Drop on the sidewalk proof. And I've proved all 3 in real world usage.

It's overkill for a bike computer. But...if you want something that's rugged and will not fail because of a sudden rain shower or it falling off the phone holder into a mud puddle, a truely rugged phone like this makes a reliable bike computer.

The ONLY advantage it has over a regular phone is that it's literally bomb proof. (I said literally. I'm not screwing around. I didn't mean figuratively. I know what I said.) It does nothing else any other Android phone can't.

The down side of 'super rugged' is that it's thick. It's hard to find a handlebar mount that holds it securely. Most have short little arms on the sides that are made to hold a thinner iPhone. This is twice as thick as my LG G5.