With today's tangle of privacy concerns, chain of custody issues, and liability issues it's a very small percentage you'll get called randomly. Your best bet is to make contacts with the LE dept and arrange for some demo flights to show what you and your equipment are capable of. Once they know you, trust you, and have faith in your equipment you might get called but I still say the odds are low to none.
Keep in mind that LE calls are a world of difference from FD and SAR calls. You have to worry about evidence, Constitutional law, and a whole slew of other issues. Also you'll need to consider Encrypted Video links if you're wanting to broadcast your video feed LIVE.