So I own a business that will soon start developing mobile apps for platforms such as the iPad. I am wondering if I can legally make a vector graphic of other companies products such as the iPad to put a photo of my application on. I will acquire an Apple Developer account and get the app(s) approved before I publish the graphics. Any insight into this would be greatly appreciated.
In general, no it is not okay.
There have been several topics here covering this:
Apple provide images of their devices that can be used for marketing purposes.
They can all be found here (requires developer log in to see): https://developer.apple.com/appstore/resources/marketing/index.html
So in your specific case, it doesn't matter... you can create an image of your app running on an iPhone or iPad, and Apple are OK with that.