I have a work assigned iphone 6, but didn't want to spend all the extra money to get the same thing from a garmin. The iphone mount is $65. Ant sensors for speed and cadence another $80. I also had the option to use an external screen that would read strava from my iphone, but at the costs of $120 I passed.

I ended up going with a used (almost new condition) garmin edge 605 for around $80 on ebay. I loaded my maps on it and it's been great and seems to be more accurate than when I use the iphone and strava. I also use an existing watch with a HR strap to monitor HR, but my device doesn't support ant so I don't have a cadence option which is fine since I'm a new rider anyway.

If you do want ant support just pick up a garmin edge 705 and use that. In the long run seems to be better and cheaper than using a phone and strava.