to confirm, is this an iPhone you are concerned about?
The only way into an iPhone this way is if your home wifi network has been hacked (or is open with no password) and your iPhone is connected to it. The best way to keep a phone secure is to keep wifi and bluetooth turned off. If you must use wifi make sure the wifi network you are connected to is using WP2-AES mode security.
On a personal note, the best way to catch malicious neighbors is with cameras, cameras, and more cameras.