If you are looking for a simple way to see all the devices on your wi-fi (local area network) and to determine who, what, when, where, how and why they connected; then, you need to take a look at Fing.
Fing is an Android App network utility designed to specifically perform a wi-fi network analysis by scanning the network that you are connected to discover what devices are (or were) connected to the network. Fing is especially useful when you need to evaluate security levels, detect intruders and resolve network issues.
Fing is a fully functional (feature rich) network utility:
+ Discovers all devices connected to a Wi-Fi network. Unlimited devices and unlimited networks, for free!
+ Displays MAC Address and device manufacturer.
+ Enter your own names, icons, notes and location
+ Full search by IP, MAC, Name, Vendor and Notes
+ History of all discovered networks.
+ Share via Twitter, Facebook, Message and E-mail
+ Service Scan: Find hundreds of open ports in a few seconds.
+ Wake On LAN: Switch on your devices from your mobile or tablet!
+ Ping and traceroute: Understand your network performances.
+ Automatic DNS lookup and reverse lookup
+ Checks the availability of Internet connection
+ Works also with hosts outside your local network
+ Tracks when a device has gone online or offline
+ Launch Apps for specific ports, such as Browser, SSH, FTP
+ Displays NetBIOS names and properties
+ Displays Bonjour info and properties
+ Supports identification by IP address for bridged networks
+ Sort by IP, MAC, Name, Vendor, State, Last Change.
+ Free of charge, no banner Ads
+ Available for iPhone, iPad and iPod Touch with retina and standard displays.
+ Integrates with Fingbox to sync and backup your customizations, merge networks with multiple access points, monitor remote networks via Fingbox Sentinels, get notifications of changes, and much more.
+ Fing is available on several other platforms, including Windows, OS X and Linux. Check them out!