A super helpful app, especially for a small Christian Community, is PrayerLincs. The app is available for both iOS and Android platforms. A group can only be joined by invitation from an admin so it maintains privacy. Once you accept the invitation you can manage your profile which includes contact information as well as some nice personality features such as interests and likes. You can view the calendar for events for the group, post messages to individuals or the whole group, post and respond to prayer requests, etc. The app is extremely useful and, best of all-free! Try it out.