Me he pasado un poco xD , pero por mas o menos 24€ si que lo tienes hecho.
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2 Reles = 5.28€ : http://www.dealextreme.com/p/arduino-5v-relay-module-blue-black-121354?item=16
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1 Arduino Nano = 11.82€ : http://www.ebay.es/itm/New-Nano-V3-0-AVR-ATmega328-P-AU-Moudle-Board-Mini-USB-Cable-FOR-Arduino-s-IDE-/180873933844?pt=BI_Electrical_Equipment_Tools&hash=item2a1ced3414#ht_726wt_706
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1 Transceptor inalambrico = 1.92€ :http://www.ebay.es/itm/NRF24L01-2-4GHz-Antenna-Wireless-Transceiver-Module-For-Arduino-Microcontroller-/140729185691?pt=LH_DefaultDomain_0&hash=item20c41cf59b#ht_1488wt_698
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Resistencias, led, interruptor, etc = 5€ (mas o menos)
24.02€