You can listen in on HAM radio and even talk from a smart phone or tablet. The format is called Echo Link. It doesn't work with all repeaters, just the ones that are active on the system. I don't know much about it because I don't use it. I'm sure if you Google Echo Link you can read for hours. You might try the QRZ.com website as well for information.
I have a hard time thinking of Echo Link as HAM radio even though many operators do. If I'm using a computer to talk to someone over the internet it doesn't seem like amateur radio activity.