We don't charge anything for GPS tracking. However, to receive text messages from your Helios Bars, you do need a SIM card. All Helios Bars come outfitted with a SIM card slot in the stem where you can easily slide in your own SIM card. We recommend getting a SIM with a pay-as-you-go plan, so you only end up paying for it when you use it. Currently the gps feature works in the US as we have not developed our module for other carriers outside the country.
A list of supported carriers will be released soon.