I use this product with the wifi turned on my phone. The GoPro app allows you to use the camera and with the latest firmware update, you can view images and videos shot. When I am at home, I just take the card out and transfer my files to my computer.
I don't own a Hero3 but I do have the Hero2 and I've used the Wi-Fi bacpac with my gopro app on my iphone and I love it. There's about a 2-3 second delay which doesn't bother me for what I'm using my camera for but it seems to bother a lot of other users.
If paired with the wifi remote (sold separately) you can turn it on and off. I use it with the smartphone app and you can control all the functions and preview and view video and photos but won't turn on and off camera at this time.
The Wifi BacPac just sets up it's own access point...any device should be able to connect to the AP. What you'll also need is the GoPro app. I think the HP Slate 7 is an Android tablet that uses the Play Store...if that's the case, yes, it should work. I've used the app on my iPad mini and Samsung Galaxy Note 2 without issue.
Per GoPro's web site ...."For Original HD HERO cameras, the Wi-Fi Combo Kit will enable remote control, but will not connect with the GoPro App." So sounds like you HAVE to get their remote control if you want to use it with the original Hero. Hope that helps.
It comes with an extension for the waterproof casing. Recently shot some underwater footage. Also recommend you to download the app for the IPad which turns your IPad into a Go Pro Monitor so you can see what your shooting underwater.