5 Popular Invention Mashups

Essential Gadget Image Gallery Mobile phones today do more than just make calls: We use them as cameras, computers, music-listening devices and GPS, among other things. See more essential gadget pictures.

When early man attached a stick to a sharpened piece of stone, he set in motion a trend in the creation of tools: the mashup. Eventually, the wheel would meet water, the transistor would meet the radio, the phone would meet the printer and airplane wings would meet the rocket.

In modern times, it's nearly impossible to touch a tool -- from watches to ballpoint pens to electric razors -- that doesn't combine at least a few different technologies.

Here, we present five of the most popular tech mashups that make work easier, playtime more fun and getting around more eco-friendly.