once we get data from the input units (sensors), how do we send this data over very long distances? i understand we can use wifi or zigbee (xbee) to send data, but will these methods work for very long distances (let's say several miles and above).
are there solutions by companies (compatible with the arduino framework) to address this problem of sending data over long distances?
Your best solution might be to get a cell-phone shield, read the data, and send the information back in either an e-mail or text message.
http://www.libelium.com/squidbee/index.php?title=New_GPRS_module_for_Arduino_(Hilo_-_Sagem)
Keep in mind, these do require a cell-phone subscription of some sort... best choice might be to get a Pre-Paid cell-phone off the shelf with like 400 minutes, and free-text messaging, but make SURE it has a SIM-card. (you need to take out the SIM-card to use that on the shield of the Arduino)
Or you can use the expensive ZigBees.. some are up to 15 miles (depends on LOS), this one is 40 miles but it's also $180
captainobvious, thanks again! let me read and research. i really appreciate your help (i must say this because i remember how brutal it was for me to post in a linux forum until ubuntu came along).
Get an Ethernet shield and hook it up to the internet. You can look at one of my Arduinos wherever you are on the planet :
but will these methods work for very long distances (let's say several miles and above).
Probably not, unless you create your own mesh network with relay stations along the way.
Some folks I've worked with have used Digi's MaxStream products for reliable links of 15 miles or so when they had good line-of-sight paths to all the sensor nodes (the "master" node was on a mountainside with a clear view of the entire valley).
Not cheap, but the network was able to work solidly in an area where there's no infrastructure: no phone, no internet, and no bars on most cellphones.
It probably wouldn't work as well in (sub)urban areas, where you have lots of buildings, and lots of activity on the 900MHz band. But there you probably have the option of using an Ethernet shield the way pluggy does.
Ran
this may be cheaper than the libelium route:
that gives you gsm connectivity, txt messaging, phone calling and a rechargeable battery for $20 =)
you might also check out www.mologogo.com, that's a little less arduino related, but might even be cheaper with the monthly rate and etc
I also suggest using an ethernet shield.