Can you take your temp with an iPhone

No.

No, you need a separate device to take your temperature.

Yes. In certain regions Apple stores require you to have your temperature taken before entering a store. You can use your phone find a store, schedule an appointment, use the navigational services to get there, and have your temperature taken there. You can also download a shopping app that will provide you list of temperature taking devices that may possibly come with an app that you can also download from the app store so your iphone can become temperature taking enabled device. Also you can use the safari browser to search and navigate to a specific website of your choice where an abundance of temperature taking devices can be purchased. Therefore your iphone can, with time and patience, provide you with a temperature measurement. There maybe a faster way.