PushCrew - Push Notifications for Websites
Pack - Makes it simple to find the best roommates.
OneSignal - Customer engagement platform used by over 1 million developers and marketers; the fastest and most reliable way to send mobile and web push notifications, in-app messages, emails, and SMS.
Roomr - Discover great people to live with
iZooto - Engage your mobile and desktop web users with intelligent web push notifications.
Spliddit - An algorithm that fairly splits rent among roommates