The phone hub has a speedo built in. You don't have to use your phone.

If you're commuting, I'd get a commuting oriented bike. There are other choices, like the Trek Verve 3, which is fast, and cheaper.

You also didn't say which 8 you were looking at.

I would broaden the search. Try a Verve, for example. Do you have a Gazelle dealer in the area? Nothing against Trek, my wife has a Verve, but if you have choices, you might as well take a look.