DAVdroid is the only all-in-one synchronization solution for both contacts and calendars based on WebDAV (CardDAV and CalDAV). The app is easy to set up and integrates perfectly with your favorite calendar/contacts app (including default apps). It can also be used seperately, if you either have CalDAV or CardDAV.
After installing the app, there will be a new account type "DAVdroid". Add a DAVdroid account using Settings/ Accounts/ Add account to enter your server. See http://davdroid.bitfire.at/configuration for help.
Important note for all Android 4.1 and all Samsung users: There's a bug that causes accounts to be lost after a device reboot. Please see https://play.google.com/store/apps/details?id=at.bitfire.davdroid.jbworkaround. For *Samsung users*: You can download DAVdroid in Samsung Store to avoid this bug.
There are issues with some HTC firmwares and contact synchronisation, see the FAQ: http://davdroid.bitfire.at/faq
вЉ› Use DAV calendars (CalDAV) and address-books (CardDAV) in a single app
вЉ› Two-way synchronization (server в†” client)
вЉ› Native Android 4+ implementation
вЉ› Flawless integration with your device and favorite apps
вЉ› Easy setup (resource auto-detection)
вЉ› Fast algorithms for high performance (CTag/ETag support)
вЉ› Optimized for phones and tablets
вЉ› Out-of-the-box support for Android 4.3
вЉ› ... and finally вЂ“ it's open source!
Get the best out of this app ...
вЉ› ... when using with your own DAV server (Radicale, DAViCal, SabreDAV, Baikal, вЂ¦) and HTTPS вЂ“ so you own and control all your data while having the comfort of synchronization between various devices. Or use a hosted DAV service you trust or the one of your company.
вЉ› ... and combine it with Evolution / Lightning / etc. on your laptop / PC
Why is it secure?
вЉ› Source code is available (see homepage)
вЉ› No need for giving your contacts/calendars to Facebook, Google, etc. Use your own server (or a trusted one)!
вЉ› SSL is recommended to protected your communication so synchronization is secure even when using open Wi-Fi networks.
вЉ› Apple's Calendar and Contacts Server