user7755: I am looking at creating a fleet of low power, Arduino driven devices.
I would need some kind of GPS on them all (or could triangulate through phone network?) plus a connection to the internet - just for HTTP POST requests. GPRS or GSM would do but 3G would be better.
What are the best (price is a major factor because I'm trying to do a fleet) GSM, GPRS or 3G modules that I can use with Arduinos? As I said, I need their location so one with GPS built in would be great.
EDIT:
The amount of devices in the fleet will change, so the entire network needs to be dynamic which is why having a GPRS/GSM module on each one would work so well.

user1675: Not many possibilities (for the phone part, I suggest a GPRS/3G shield), but not wanting to discourage you, if you are thinking about "a fleet", forget about:
low power (the phone radio needs power, some say you need > 1A for both Arduino plus the shield, depending on your distance to the antenna). you must add the GPS part. Even if you communicate just a fraction of the time, you need instant power for feeding the radio.
low price (gprs shields are not cheap, starting at some 25€, and gps shields about 20€). and don't forget that you need a SIM card with a data plan for every unit....

Depending on what are you trying to achieve, I'd try with less expensive (RF communications, for example) to avoid carrier costs and hardware costs, at the price of a more complex development. If you want to publish to a web service, you can always make your minions transmit to a centralized Raspberry PI, for example, that would take the task of bridging with the Internets, or your mastermind...:-D

user7642: If you are finding Cheapest and working module you can you SIM800L less then 4$. 

aliexpress.com/item/Free-Shipping-Smallest-SIM800L-GPRS-GSM-Module-MicroSIM-Card-Core-BOard-Quad-band-TTL-Serial-Port/32708504554.html

You can find many other cheap alternative but they does not work properly.
Sim800 have good support and you can find many examples to use this with arduino.
Many other model also available in market as per your requirements.   

7755: <p>I am looking at creating a fleet of low power, Arduino driven devices.</p>

<p>I would need some kind of GPS on them all (or could triangulate through phone network?) plus a connection to the internet - just for HTTP POST requests. GPRS or GSM would do but 3G would be better.</p>

<p>What are the best (price is a major factor because I'm trying to do a fleet) GSM, GPRS or 3G modules that I can use with Arduinos? As I said, I need their location so one with GPS built in would be great.</p>

<p>EDIT:
The amount of devices in the fleet will change, so the entire network needs to be dynamic which is why having a GPRS/GSM module on each one would work so well.</p>
 1675: <p>Not many possibilities (for the phone part, I suggest a GPRS/3G shield), but not wanting to discourage you, if you are thinking about "a fleet", forget about:
<li>low power (the phone radio needs power, some say you need > 1A for both Arduino plus the shield, depending on your distance to the antenna). you must add the GPS part. Even if you communicate just a fraction of the time, you need instant power for feeding the radio.
<li>low price (gprs shields are not cheap, starting at some 25€, and gps shields about 20€). and don't forget that you need a SIM card with a data plan for every unit....
<br><br>
Depending on what are you trying to achieve, I'd try with less expensive (RF communications, for example) to avoid carrier costs and hardware costs, at the price of a more complex development. <br>If you want to publish to a web service, you can always make your minions transmit to a centralized Raspberry PI, for example, that would take the task of bridging with the Internets, or your mastermind...:-D</p>
 7642: <p>If you are finding Cheapest and working module you can you SIM800L less then 4$. </p>

<p><a href="https://i.stack.imgur.com/YtyoZ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YtyoZ.jpg" alt="Sim800L"></a></p>

<pre><code>aliexpress.com/item/Free-Shipping-Smallest-SIM800L-GPRS-GSM-Module-MicroSIM-Card-Core-BOard-Quad-band-TTL-Serial-Port/32708504554.html
</code></pre>

<p>You can find many other cheap alternative but they does not work properly.</p>

<p>Sim800 have good support and you can find many examples to use this with arduino.</p>

<p>Many other model also available in market as per your requirements.   </p>
