There are currently about 3.2 billion mobile subscribers in the world, and that number is expected to grow by at least a billion in the next few years. Today, mobile phones are more prevalent than cars (about 800 million registered vehicles in the world) and credit cards (only 1.4 billion of those). While it took 100 years for landline phones to spread to more than 80% of the countries in the world, their wireless descendants did it in 16. And fewer teens are wearing watches now because they use their phones to tell time instead. So it's safe to say that the mobile phone may be the most prolific consumer product ever invented.

However, have you ever considered just exactly how powerful these ubiquitous devices are? The phone that you have in your pocket, pack, or handbag is probably ten times more powerful than the PC you had on your desk only 8 or 9 years ago (assuming you even had a PC; most mobile users never have). It has a range of sensors that would do a martian lander proud: a clock, power sensor (how low is that battery?), thermometer (because batteries charge poorly at low temperatures), and light meter (to determine screen backlighting) on the more basic phones; a location sensor, accelerometer (detects vector and velocity of motion), and maybe even a compass on more advanced ones. And most importantly, it is by its very nature always connected.