Hi @iffatkhannn and thanks for your query. I assume you are referring to include eye tracking into a similar software as Document Writer?
For the time being, we do not have a software development kit that targets iOS, but if you are interested in Windows development for PC and tablets, then checkout the Tobii Core SDK @ https://developer.tobii.com/consumer-eye-trackers/core-sdk/ which is designed to operate with the consumer level eye trackers such as the Tobii 4C and EyeX.
In any event, if you could kindly be more explicit in your project intentions with relation to eye tracking, we would be happy to assist further.