Most earbuds are designed for use while mobile; after all, they're inherently more portable and discrete than headphones. But not all of them are made for heavy activity. Ever try running or hitting the gym with most off-the-shelf 'buds? I have, for years. It's usually not an enjoyable experience. They need to meet some pretty specific criteria:
Last month I reviewed of the a-JAYS One+ earbuds, and came away impressed. For $50, they packed quality sound and impressive bass into a sleek, attractive form, in addition to a trick control button/mic built into the cable. Coupled with the JAYS app, the button controls your phone and music player, allowing you to play, pause, change tracks, adjust the volume, and take calls - certainly making usage more convenient than typical earbuds.
These days, earbuds are a dime a dozen - they can be had for as little as $1 at the dollar store, all the way into the hundreds of dollars for a high-end pair. And sound quality has improved quite a bit since the early days - any buds that are mid-range or better usually offer pretty good sound, so they're differentiated as much by features as by sound quality. That's where the $50 a-JAYS One+ headphones come through: features. In this case, the largest selling point (that gives it that little "+" in the name) is the inclusion of a control button.