SparkFun Forums

[rrc1962]

A comment on the cell shield page points to this website to purchase a card Bu so far no one is stepping up and saying "Yes it works and here's how I did it".

http://www.embeddedworks.net/psummary.p ... =mwsim4005

I think a cell interface would be easier, but I see no indication that it actually works. In my application, internet is not an option because the sensors are mobile and need to send a text message when an out-of-range condition occurs. If I can buy a card for around $100/year, that's a workable solution. I guess I just need to buy one and try it.

[stevech]

Cell service for one-of will cost at least $35 per month.

[mikecyber]

http://www.sparkfun.com/products/9607 works fine in the US. AT&T and T-Mobile both use GSM bands, the SM5100B is Quadband, and will work in the US and most everywhere else. It's capable of making calls, sending texts, and GPRS connectivity. Details on anything other than the very basic pass through sketch provided by SF are sparse, however, there are libraries written for other hardware that can be re-purposed.
http://code.google.com/p/gsm-playground/updates/list is a library written for the GSM Playground, http://www.hwkitchen.com/products/gsm-playground/, but if you replace Serial with Serial1, ensure the library doesn't change the baud rates, put it on an Arduino Mega, and place jumper wires from Serial1 to pins 2 and 3, most of its functions will work without modification. It does use commands for a telit gsm unit that aren't compatible with the SM5100B but all you need to do is go through the respective AT command sets and find equivalents.
http://code.google.com/p/sserial2mobile/ is a library written to communicate with cheap go-phone type phones that use a serial connection. Some phones are capable of communicating via the headphone jack. The command set is more limited than hwkitchen's but it also mostly works.

You will need to provide your own SIM card, T-Mobile will give you one for free if you buy $30 of airtime. $30 will last for many messages, or 3 months, whichever happens first. AT&T has a deal where you pay $1-$2/day that you use the phone, with unlimited usage. So if you only use it for 10 days in the month, you only pay for 10 days.

[mikecyber]

You will need to provide your own SIM card, T-Mobile will give you one for free if you buy $30 of airtime. $30 will last for many messages, or 3 months, whichever happens first. AT&T has a deal where you pay $1-$2/day that you use the phone, with unlimited usage. So if you only use it for 10 days in the month, you only pay for 10 days.

The AT&T deal is by far the better choice, as you can use GPRS with your prepaid account. They charge $0.01 per KB. T-Mobile has discontinued this option, in favor of charging $2 per day for "unlimited" internet access, on top of your prepaid amount.