The Scarab range of wireless modems allow bi-directional data communication over the radio. There were several versions offering various speed/range/price trade-offs offered by New Era Microsystems. The model I was using for this 1.2km link is the Scarab Beetle Soft Modem, which has a range of 20km at 9600 baud on one of 16 licence-exempt channels around 458MHz.
New Era, the company I dealt with, has ceased operations since its founder, Mike Jessop, emigrated to Australia. The business and its products were acquired by LinkUp International. I do not know if the Scarab range is still available from them.
I have no commercial connection with the makers of the Scarab modems, except that they loaned me some of their units while I was developing a Linux driver for the modems. The source code for the latest version of this driver is available here.
Another project is an 802.11 wireless LAN driver for the fastest model in the range, the Scarab Aether, which uses a 2.45GHz spread-spectrum transmitter to achieve 1Mbaud. The existing driver works well with this model at 960kbaud and achieves an effective throughput of about 700kbaud with mostly unidirectional IP traffic (like an FTP download) but only about 100kbaud with bidirectional traffic because the driver has a very simple scheduling strategy that tends to trigger TCP back-off.
The same driver will also drive the Adaptec Airport, a useful gadget that adds an infra-red output to an ordinary PC serial port.