I know the official requirement to use the Apple Watch is an iPhone 5 or newer running iOS 8.2+, but I'm interested to know if it is possible to sync it to an older iPhone, iPod, or an iPad by side loading the Apple Watch app or any hacks. According to Bluetooth SIG's site the iPhone 4s, iPad (Air, Mini, 3rd & 4th gen), and iPod touch (5th) are Bluetooth Smart Ready which means they are compatible with both standard and low energy Bluetooth protocols. Since the Apple Watch only works with Bluetooth LE and these devices also support LE it seems to be just a software limitation.
I would try side loading the 'Apple Watch' app myself to a jailbroken iOS device however I am not able to find a .app/.ipa for it.
I have already read the "Can you use the Apple Watch with an iPod touch?" post but I believe this question is different enough to justify a new thread.
Best Answer
Apple Watch uses Bluetooth to communicate with iPhone. iPhone 5 is the first device that had Bluetooth LE support, which is used in cases where you want a low-energy-usage always-on connection, so it would follow that is the earliest model that can actually communicate with Apple Watch.
While Apple Watch can, in some circumstances, use Wi-Fi to communicate with iPhone, it has to be a network that iPhone was connected to while previously paired with Apple Watch over Bluetooth. Since devices prior to iPhone 5 likely cannot establish a Bluetooth connection to Apple Watch, no Wi-Fi network would ever be trusted by Apple Watch to use for communication with iPhone.