OwnTracks has a so-called Friends and Family capability which is enabled by default. The way this works is friends and/or family members who share a single MQTT broker can "see" eachother on the map, respectively on a list of friends held by the app. (This can be done either by configuring all apps to use the same broker or by what is called bridging.)
Let's assume for a moment, that a user Jane (user name
jjolie) has an iPhone 4s (device name
4s), and that she publishes location data to a topic at
Let us further assume, that her friend John (user name
john) has an Android Nexus 4 (device name
nex4) and he therefore publishes on the same broker to a topic called
Let us further assume that access control on the MQTT broker allows both users to subscribe to eachother's topics.
Now, if both friends subscribe to a topic called
owntracks/+/+ (which the
apps do by default) their devices will effectively receive published location
messages to either topic. So when either Jane or John publish their location,
the other's device will receive it.
What OwnTracks then does is to list these topic names (e.g.
owntracks/jjolie/4s) with the last received position and a time stamp. A click on a particular entry will take you to that entry's location on the map. Neat, eh?
It gets better.
You probably don't want to remember the (sometimes cryptic) topic names of your friends or family members, but you would like to see their names and a matching face. That's no problem: OwnTracks can do that.
Depending on the device you're using, the procedure differs slightly.
The app subscribes to a topic branch
owntracks/+/+ on the broker per default
to receive locations of
other people connected to the the same MQTT broker that publish
to the default topic of
It then reads CARDs to find friends' names and faces.
The app "sees" a friend as soon as it receives a publish to the topic branch subscribed to, which by default is
Select the Friends button to see a list of friends:
Tapping on one of the friends, performs a reverse geo-coding to show address. Furthermore, a click on the little right-arrow shows their last location.
Who is that?
It's difficult to remember which MQTT topic belongs to which friend, so we can associate a topic with an image of the friend as contained in the iOS address book:
Select an entrythen click on the bookmark icon on top right. The Address book opens.
Select the entry you want to associate with the OwnTracks topic. If you want to release the association, select the wastepaper basket icon in the address book screen. The display changes back from the picture and name of the friend to the mqtt topic (e.g. "owntracks/kate/nexus4").
When you zoom the map out (or near to the friend's location), you see a small rendition of the icon directly on the map.
Note: this works only with contacts stored locally -- not with corporate address books associated with your iPhone.
To support corporate address books (which usually cannot be updated) the ios
app Version >=5.1 can be set to store the associations locally rather than in
the address book. You find the respective switch in the expert mode settings.
off (i.e. disabled) to keep associations between MQTT topics and
your contact within OwnTracks.