Firstly, don't let them strong arm you - most patent trolls blast complaints like this to many parties at once and hope a percent of them cave without the need for court.
If this did go to court, I strongly doubt you would be found guilty of infringing on these patents. Based on your statement, it sounds like you simply made an app that converts third party API data to a UI, which wouldn't come close to either patents as they are related to the actual process of tracking vehicles, which the API provider partakes in, not you.
I would simply contact them and let them know that you don't track them yourself, you use another company. Most lawyers don't understand software, so they might be assuming you are tracking vehicles on your own. If they continue to press you past that, you might be forced to take it to court.
Best of luck and please keep us informed.