When looking at open protocol wireless solutions (802.11X), GREGTHESUPERTECH’s posting is somewhat correct. But, you can get more secure wireless connections for point to point.
Look into the Motorola Canopy radio. They make a point to point back haul radio that is totally integrated into one out door package. The unit is powered over the Ethernet cable via a supplied adaptor (we use out-door rated CAT-5e cable). The back haul radios are available in 10 Mbit and 20 Mbit full duplex models, and can be much cheaper than leased T1 circuits.
We have been using these radios for point to point inter-office networking for a while now, and they work great.
FYI, they also make a point to multi-point model, available at a lower data rate.