What white noise machine do you use?

What white noise machine do you guys use? I’m currently using an old iPhone with an app I downloaded but the phone died last night in the middle of the night and I didn’t notice until this morning. I’d like to invest in an actual machine and use the old phone for backup or emergency when the power is out.

I’m also currently using the old school sound baby monitors but I plan on also investing in a baby monitor camera.

Also, how long do you use these for? 2 years? 18 months? I plan on having more kids anyway so I will be using them for awhile but at what age do you stop?

Thanks!!