New kickstarter project - WiLoader.
WiLoader is fully supported in Arduino IDE. Easily, you can upload your code to your project with Arduino (AVR) through WiFi.
WiLoader has WiFi-UART bridge called WiCOM.

The price of base board is $29 - only WiLoader and headers.
For $49 you get programmer + EVK pack (Mini Breadboard, ATMega328P, crystal, resistors, PIR sensor and another components for development).

Website of project: http://wiloader.com/

Website of campaign: https://www.kickstarter.com/projects/petuniatech/wiloader-the-wifi-programmer-for-avr