I don't know where you live nor how much electronics gadgets would cost you at home, but here's my experience...
1.) Bring a smartphone. iPhone or Blackberry or anything else doesn't matter as long as it has a web browser. If it has GPS that helps even further if you're not familiar or confident about the local streets. Make sure that it's unlocked and tri- or quad-band GSM so that you can use it in Hong Kong. China Mobile, Peoples and 3 should all work. 3 is $248 HKD I think? Buy a sim card with 1 month prepaid data plan at the airport before you leave.
2.) Bring a netbook. Okay, this is optional. I brought my iPad and it was rubbish trying to write reports and you can't upload photos on it. I'll likely buy a 10" or 11" netbook on my next travel. My iPhone is actually enough but I buy a lot of gadgets already because I'm a guy and can't control myself
Actually, having a netbook is great for watching movies while on the plane and during down time in your hotel room.