Founded in 1998 by evangelical Christian Dr. Neil Clark Warren, eHarmony was the first and most popular of the test-based matchmaking sites and welcomes more than 10,000 new users a day to its pool of 6 million singles. The. Integration with Foursquare allows you to search for date spots and get recommendations. Datebook is available only on eHarmony’s mobile app, which is free to download as long as you register…