Twitter developers are now working on a GPS tracking system that will provide accurate information on your whereabouts (or your kids). Users will be able to add GPS co-ordinates to any tweet. Apparently the option will definitely be opt-in. This new feature will need to activated by choice and they claim the exact location data won't be stored for an extended period of time. Unfortunately what tends to happen is once the data is available on the internet it is there for good. You can bet third party services will use the data and offer it to anyone who is willing to pay.