crowsonkb

Actually, LE isn't even necessary. I found this article on Logic Remote which acts as a sort of companion iPad app for Logic Pro, and was able to use the steps in it to control Alfred on my Mac from my iPad with WiFi off: http://support.apple.com/en-us/HT202765 This apparently sets up a Bluetooth personal area network where both devices get self-assigned IPs in the same subnet and mDNS works as usual for service discovery. I'm using Yosemite and iOS 8 so I don't know how far back this works but as of the current OS releases it seems to work 'out of the box' already.

Seconded. Bluetooth 4.0/Bluetooth LE is an incredible leap forward for this sort of thing. Apple is using it as the backend for Continuity and a number of other things but they've opened up the Core Bluetooth framework for us to use: https://developer.apple.com/library/ios/documentation/NetworkingInternetWeb/Conceptual/CoreBluetooth_concepts/AboutCoreBluetooth/Introduction.html#//apple_ref/doc/uid/TP40013257 There's an app called 'MIDI LE' for example on the App Store that lets me plug a USB MIDI keyboard into my phone and use MIDI-over-Bluetooth-4.0 on Logic Pro on my Mac (without any sort of having to be on the same wifi network of course). It also isn't using old-style Bluetooth personal area networking; it's an entirely new very low-latency non-TCP/IP-based thing. As a further example Apple is using Bluetooth LE to scan for nearby paired iPhones and iPads which are then commanded to turn on a higher-bandwidth WiFi link and that's how tethering has been working in Yosemite/iOS 8.