Soon, you might be able to run WhatsApp on four smartphones simultaneously
Multiple device support is a long awaited feature on WhatsApp. And, it will soon become reality with users able to run the same WhatsApp account on four different smartphones at the same time. As of now, WhatsApp only allows you to operate an account on one smartphone.
The feature is still under works and is being tested by WhatsApp so is not available for public use. Source - Reuters.