Agasa-hakase's Story
Agasa-hakase is Shinichi’s closest neighbor and “friend”. “Inventor of useless crap” is how Shinichi describes him (page 11 of case 2) – well, Shinichi was in anger at that time… being the first person to realize that Conan is actually Shinichi, Agasa helps Conan out a lot by making useful inventions (proves Shinichi wrong, by the way.) The mini-stun-gun watch, bowtie voice-changer, and the power shoes are just some of the inventions he has made for Conan, and these gadgets help Conan a lot when it comes to solving cases.

About Agasa-hakase
Agasa-hakase works on experiments at his home, and makes $$$ from new inventions. (Not the kind NEAR the ones Conan has) While not stuffing his face on inventions, Agasa-hakase likes to go surf the internet. He owns a yellow VW bug.
It is obvious that Agasa loves kids a lot, because he likes to hang out with Conan's new little kid friends, the Detective Boys. He possesses a very kind heart. However, he doesn't like to think of himself as old...even though he's almost bald...

Friends & Family
Agasa-hakase lives by himself, and doesn’t have any close relatives. His best friend would probably be Shinichi. After Shinichi has become Conan, and made friend with Yoshida Ayumi, Kojima Genta, and Tsburaya Mitsuhiko, Agasa-hakase also become friend with the 3 elementary kids, and many times drives them out of town for field trips (usually for mystery cases which he thinks they would like, since they are the Detective Boys). They sort of become family to him.
Later on in the story, Haibara Ai (formerly Miyano Shiho), who has also turned into a child because of APTX-4869, moves in Agasa's house because she was alone and he took her in. Just more reinforcements of his kindness.