iPhone 4 and Mobile Power Station

When I had my iPhone 3GS with the short battery life, I had ordered a Mobile Power Station to keep it going all day while at work. At work I stream audio all day and it really drains the battery. I've been off work since I got my iPhone 4, but I'm returning next week. What I'm wondering is if this little power pack can damage my iPhone 4? I've had no battery issues at home, but I'm not doing any streaming.

The Mobile Power Station has a 1000mAh capacity and an output of 5V/500mA (whatever that means) :confused: