MyWi, a popular app available in Cydia that allows users to turn their 3G-capable devices into mobile hotspots for internet tethering, was updated today to include a new functionality the Intelliborn developers call "On Demand". The new feature, which can be unlocked for $4.99 following the $19.99 app purchase, allows iPhones and iPads to "understand" when the mobile hotspot feature needs to be activated, or disabled.
A problem with mobile hotspots on the iPhone, in fact, is that you can't specify settings for when a WiFi connection becomes available and you can stop tethering to other devices. The new MyWi On Demand connects when you need it, and shuts down when you don't. After the usual pairing session between the hotspot device (say, the iPhone) and a non-3G device like your iPad WiFi, the iPad will automatically join the internet connection shared by MyWi when no other option is available, and disconnect from MyWi when another connection is found (your home wireless connection, for example). The system is pretty smart and useful, especially considering that it easily lets you save dozens of MBs of data.
More details on MyWi On Demand can be found here, and you can check out the promo video below. Apple's next major update to iOS, version 4.3, will introduce a similar functionality called "Personal Hotspot" that enables users to turn their iPhones into portable hotspots to share an internet connection.