Transmitter/Receiver

yes gprs

yes gprs receiver

or even possibly Blue tooth for such a short range.

or even a wireless modem. any good

http://www.google.co.uk/search?q=gprs+data+transmission&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=UCSWTID9Lo_KjAfa_YDGBQ

http://www.google.co.uk/search?q=wireless+remote+programable+message++signs&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=jyaWTKGwEpWSjAfPm7HcBQ

http://www.google.co.uk/search?q=gprs+data+transmission+receiver&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=fiSWTOj3Hpi8jAfF14zzBQ

http://www.google.co.uk/search?q=short+range+data+transmission&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=oCSWTO6qDtC6jAem4cS1BQ

http://www.google.co.uk/search?q=remote+programable+message++signs&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=GSaWTO-wH8OOjAfulsScBQ

http://www.ledsignage.com/newprod.htm

en.wikipedia.org/wiki/Digital_signage_product_comparison - Cached - Similar

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Since you wish this to be solar powered, you will have to also have to include some energy storage for the solar power that will carry this through the night. Because of this I recommend you abandon the concept of continuous transmission and reception and switch to the idea of transmission bursts to save power. Now this could be bursts that happen so frequently that a person would perceive this as continuous but to actually do a continuous will maximize your power load.

Solar array, battery pack, Arduino board, plus one of the following:

Bluetooth

WiFi

EasyRadio

HomeEasy

HopeRF

Infrared

VirtualWire

X10 Wireless

XBee/Zigbee

module(s) for Arduino. Obviously, the battery source would have to be optimized to last through nights and cloudy days.

See HERE for more detailed info for Arduino RF operation. One or both can be transmitter, receiver, or transceiver.

Hooker