Q: The Apple “Find My Friends” app doesn’t seem to be working properly for my partner and I. We’ve both installed it and set it up on each of our iPhones and my iPad, and I can find her accurately almost all the time from either of my devices, but when she looks for me I’m almost always showing at home, even when I’m several miles away. Weirder yet, this isn’t always the case… it seems to be hit or miss as to whether she gets my actual location or simply my house. Any ideas?
– Sara

A: The most likely cause of this behaviour is that Find My Friends is using the location from your iPad instead of your iPhone.
If you’re leaving your iPad at home, and it’s turned on and connected to a Wi-Fi or cellular network, then anybody querying your current location is going to get the location reported by your iPad instead of your iPhone.
You can control which device is used to transmit your location by opening the Find My Friends app on any of your devices, going to the Me tab and then tapping on the Accounts button near the top-left corner.
From here you can also swipe-to-delete to remove devices from this list that you are no longer using—particularly useful if you’ve upgraded or replaced an iOS device. Find My Friends uses your device’s physical hardware ID, so when you set it up on a replacement device, even if you restore your backup, it registers as a new device.
The device you’re currently using will be indicated by the words “(This Device)” beside the name; feel free to remove any other entries that appear here with the same name as long as you’re sure they don’t actually represent other iOS devices.
Note that although Apple’s support documentation on Find My Friends suggests that your location will only ever be reported from the “Active Device” listed on this screen, in our experience it does appear that if your primary device is unreachable, Find My Friends will sometimes fall back to using a location from one of your other iOS devices. This does not appear to be consistent and in light of Apple’s own support documentation may simply be a bug as opposed to an intentional feature.
Keep in mind as well that unlike most other location-based apps such as Google Latitude, the Find My Friends app does not update your location automatically; location is only reported by your device when one of your friends actually requests it.