Originally Posted by
WalksOn2Wheels
The DuoTrap S will not fit into the old DuoTrap slot.
My short answer is to look into the Wahoo Rflkt. I'm a Garmin guy, so I've never used the Wahoo stuff, but it would be within your proposed budget and should do what you want.
This! I've been using one for two years with Cyclemeter on my iPhone 5c and haven't looked back. Since your DuoTrap is BT, you won't need the RFLKT+, which has the Ant+ bridge. The RFLKT displays all of your ride data on default or customized screen pages so you can keep the phone in standby mode and only turn it on if you want to see the map page of your phone app. BTW, your Strava app does work with the RFLKT.