Considering how long my smartphone battery lasts when WiFi is on (and assuming it has reasonably low-power circuitry), I seriously doubt it is possible to have year-long lifetime on AAA battery, unless you want the module to spend it in deep sleep mode (where it is certainly possible to achieve consumption in µA range).
Just to put things into perspective, [randomly picked] RN-171 ultra low power 802.11 b/g module has power consumption 35 mA active RX, 180 mA TX (at +12dBm). The capacity of Sanyo Eneloop AAA 1.2 V battery is 800 mAh, which means theoretically 800/180 = 4.4 hours of full power transmit operation (not including receiver, the power consumption of the rest of the module circuitry, losses etc.). To get year lifetime, the module would be allowed to transmit for 500µs 1.8 s every hour (4.4/365/24*3600).
The extremely long run time implies extremely low data rate and short range (low power), you'd probably need to do some research in areas suggested by mHammer, i.e. Bluetooth Low Energy, ZigBee or custom RF modules (like nRF24 or similar).
Edit: After I corrected the formula, it seems it could be done after all (?)
Edited by CW2, 26 March 2013 - 04:10 PM.