I received the Pacsafe Luggage Venturesafe 32l Travel Backpack from ebags (more on that later) and I am very impressed with the bag.
The bag looks like a conventional backpack until you start looking closer.
The Backpack has security features everywhere, such as zippers that clip to a fixed point on the bag (to prevent pick pockets) and straps that have steel wires thru them so they can't be slashed and there are clips that have locks on them on the straps that can be secured to a table etc.
Additionally the bag has a type of steel mesh running thru the skin of the bag which will prevent someone slashing your bag and spilling the contents.
All of this steel adds very little weight but a TREMENDOUS amount of security!
As for ebags, the Amazon seller I got the bag from, let me just says this, skip them!
I payed for expedited shipping (32.90) and they did not provide a tracking number (despite an email asking for it) and there customer service is terrible!
Do your self a favor and buy from someone else, it will be cheaper, and you will get better customer service.