I know that Apple Watch apps can not be standalone. But my issue is that I want to give out Apple watches to research subjects say In a hospital or athletes at a track meet and monitor their heart rates. They do not have iPhones. The watch is the primary device of interest and I am providing an Apple Watch to them. Can I do this? Say get each Apple Watch user’s heart rate and upload it to my server? Or do I have to also buy 100 iPhones to give to each person? What’s the max number of watches that can be paired with a single iPhone and be in use simultaneously and treated as a separate watch by the iPhone?
Paulw11 is not quite correct. A watch doesn't need to be in range of its paired phone in order to connect to a server. When the phone is switched off or out of bluetooth range, the watch will quite happily connect to any preconfigured WIFI. Of course an LTE Apple Watch can also connect using Cellular.