Linksys, Netgear, Sonicwall, Cisco, just about any wireless access point/router should work over that distance, speed dependent on wireless protocol. 802.11b runs up to 11Mbps, slightly faster than 10bT ethernet, 802.11g runs at 54 Mbps, about half of 100bTX ethernet.

VoIP might be somewhat expensive depending on how many extensions. Check into some long-range cordless phones, Engenius makes some that will reach that far easily.

Joe
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No trees were harmed as a result of this posting; however, many electrons were severely inconvenienced.