We'll look into a way to add more multi contact options in the future, but for the time being you can edit the existing options to launch any URL you want. For instance, you can update the Mail icon to launch your favorite mail client instead.
To do this, first enable the "Show URL on launcher edit" switch in the Options -> Global Settings menu.
Then edit a launcher to email your friend with your favorite email client. Copy the URL in the URL field.
Then edit the multi contact launcher you want to update. Delete the existing Mail row, if any, and add a new Custom Launcher row. In the URL field, paste the URL you copied from the other launcher. Tap on the icon to change it to the mail icon.
An iBeacon is a device that emits a signal which can be received by your iOS device. Starting in Launcher v2.1, you can use proximity to an iBeacon device to show or hide a launcher widget. This is similar to setting a widget to show or hide based on a location on a map, but because an iBeacon has a limited signal range, it can be used to define smaller area ranges to set the visibility of a widget. Some iBeacons are also portable.
This means that you can use an iBeacon to show or hide a Launcher widget in different areas of a large home or office. Or you can put an iBeacon in your car so that you can have a widget that only appears when you are inside it.
Note that there are many iBeacons on the market, but only iBeacons that expose (or let you set) their Proximity UUIDs can be used with Launcher. We recommend Rad Beacons by Radius Networks as a decent, cost effective iBeacon solution that is compatible with Launcher. They can be purchased through Amazon, other retailers, or their own website.