Bing just announced an app for Windows Phone called â€œWeâ€™re Inâ€. It helps people when planning their road trip or meeting among friend at some places, etc.
App Description from Bing blog,
Weâ€™ve made Weâ€™re In super simple to use â€“ all you need is your phone number to sign up. Simply invite your friends (via your contacts) to start sharing location info with each other including who, why, and how long:
Pick your friends from the contact list or enter their phone number, tell them what the plan is. At this point you can choose how long you want to share location info.
Your friends receive a text message with these details. They can use the app to join you or, for friends that don’t have a Windows Phone, they can join from the mobile website via the invite.
Once your friends have joined you on the place, they will appear on the maps as seen in the screenshot above. You can update status of your own to notify your friends on whatâ€™s going on..Your friends can view that by just tapping your photo on the map.
Update: The app is available only in US.