If you get a 3G Wifi Router you can hook your PS3 to it but i don't recommend using WWAN for gaming due to ping and packet loss issues that they have.
Their are 3G Routers from D-Link and Netcomm.
D-Link
http://www.dlink.com.au/products/?pid=525
Netcomm
http://www.netcomm.com.au/netcomm-products/voip/3g18wv
This netcomm router is small(pocket sized)
http://www.netcomm.com.au/netcomm-products/3g-mobile-broadband/3g24w
I think you can bridge a connection from your laptop to the PS3 via an ethernet cable. Look for tutorials, I'm not too sure how to do it myself.
Why does it have to be wifi? And would this product do the trick?
http://dicksmith.com.au/product/XH1441/wireless-3g-mobile-broadband-router
I'm new to all this stuff..
That has ethernet and wifi.
The 3G18WV is a 4 port router with wifi and it also has VoIP(if you ever want to use it).
The DIR-451 is 4 port router with wifi.
With wifi it means you can connect your PS3 to it with via Wifi or connect any laptop in the house to it.