I/Os provide interoperability between devices, however an Application Programming Interface (API) is what allows interoperability between software. With all devices, there is one critical resource generated which is data. This data that is generated through temperature scanning, facial recognition, time, date and other parameters become important data points that you would want to feed into other reporting systems within your organisation. In order to facilitate this, it is important to understand if the software is API ready so that you are able to integrate it to 3rd party systems for data sharing. Take for example your HR system requires data from the thermal scanner, if there are ready APIs, it is possible to automate this data sharing by integrating the 2 systems.
Not all software out there is API ready and one should make sure that the thermal scanner and the provider are vetted before purchasing to ensure that should you want to scale the use of it that a.) it is API ready and b.) the vendor can advise you on this.