Now that iOS 8.1 is out, with iOS 8.1 running on your iPhone, you can use your iPhone as a Instant Hotspot for your Mac (running Yosemite) and for your iPad or iPod Touch (also running iOS 8.1). This is one of the features of Continuity, which further integrates and connects your Mac and iOS devices. Continuity also includes Handoff, iPhone Cellular Calls, SMS Relay, and AirDrop.
When you are in an area with your Mac, iPad or iPod Touch that does not have Wi-Fi, they can connect to your phone’s personal hotspot when your iPhone is nearby. Now you do not even have to set up a personal hotspot on your iPhone and enter in the Wi-Fi Password for your personal hotspot. When you join the Wi-Fi network on your Mac, iPad or iPod Touch, the name of your phone will be listed automatically. All you have to do is join it. When you aren’t using your phone’s hotspot, your device will disconnect automatically to save battery life. Your device will remember the fact that you used your phone’s hotspot and the next time you want to go online when you do not have Wi-Fi, it automatically rejoins the hotspot.