Our customer always demand, and I think there is huge market of, live tracking data. We need to ease either our customers or their relatives that they have reached their destination safely. So as I was moving around, I found out that there are too many live data APIs, but I want to integrate the free live API in order to check first. Can any one give me options that provide live APIs? Also if I need to get ADS-B what can I do and how does it work?
There are numerous web sites that provide flight tracking data, including radar and ADS-B. Most are free for personal use, but AFAIK all of them charge for commercial use. This makes sense since collecting and aggregating that data takes a lot of time, effort and equipment, and they have to recover those costs somehow. Still, using an existing service should be a lot less expensive than trying to set up your own redundant operation just for your own needs.
The sole exception is if you're trying to track ADS-B flights in the vicinity of your own facility, in which case you can easily set up a single ADS-B receiver there. But most folks want a (much) bigger picture, including non-ADS-B traffic, so please clarify the scope of your needs.
On the ADS-B side of things, if your looking for a purely personal system at receiving ADS-B, a Raspberry Pi 3b, a USB dongle (RTL2382 version), a antenna and some coax - install Dump1090 onto the Pi and your in action. Not this simple but a basic overview.
If you are looking for a turn-key 'plug and play' solution you might want to check out VariFlight (VariFlight ADS-B) , they often provide free ADS-B systems with everything you need, you just plug it in and go. The only requirement is you have the ADS-B receiver connected to the internet to feed them the data you are receiving.