Meitrack.
Keep in mind that if you buy another brand, I can't guarantee that it will work with the tracking website. If you only want to use SMS and not the tracking website, then you can buy whatever you like.
Also if you prefer to deal in Australia, the company I'm currently working for (but leaving at the end of this week) has the MVT380 which has a few more functions available. http://www.meitrack.net/mvt380
I will still be helping STS out with this product even though I'm leaving.
The MVT380 is $150 ex GST and postage.
We've been talking about doing a cheap monthly/yearly tracking price for Mustangtech users. But this "club rate" would mean no "official" support - only support via the forum between other tracker users.
We've been thinking about a yearly fee of $200 - thoughts?
Yes, you need a sim card for it to send SMS, or GPRS (internet) data or both.
If you want to be able to locate your device on a map, then you need to pay for a service such as the one STS is offering. Your device will check in to the server via GPRS/internet over a time interval that you set. So you can see where the vehicle has travelled, the speeds it was doing etc.
If you only want to operate it via SMS, then you don't need to pay for a tracking service. You just pay or your sim card and that's it. You can send a command via SMS and it will send you it's current location or last known location.
I have a free server that I run at home too that can also be used, but it's only good for mapping. It can't send commands to the device etc. As it's only running on my home server and internet connection I can't give any service guarantees (aside from the fact that it's free).