Use AirDrop between iPhone and older Macs (need "Don't see who you're looking for?" button on Mac)

From Apple Support:

What you need To share content with AirDrop, both people need one of these devices using iOS 7 or later, or a Mac with OS X Yosemite:

• iPhone 5 or later
• iPad (4th generation) or later
• iPad mini
• iPod touch (5th generation or later)

System Requirements

To see if your Mac works with AirDrop, make sure you’re in the Finder by clicking the desktop (the background area of your screen), or by clicking the Finder icon in the Dock. Then, check to see if AirDrop is listed as an option in the Go menu. If you don't see AirDrop listed, your Mac doesn't support this feature.

In order to transfer files between a Mac and and an iPhone, iPad or iPod touch

• Your iOS device needs to include a lightning connector
• Your iOS device needs iOS 7 or later installed
• Your Mac needs to be a 2012 or later model with OS X Yosemite installed
• Your Mac and iOS device both need bluetooth and Wi-Fi turned on. You do not have to be connected to a specific Wi-Fi network.

The Mac Pro (Mid 2012) does not support AirDrop with iOS devices.

To transfer files between two Mac computers, you need the Mac models listed below with Wi-Fi turned on and OS X Lion or later installed. MacBook Pro (Late 2008 or newer)** MacBook Air (Late 2010 or newer) MacBook (Late 2008 or newer)** iMac (Early 2009 or newer) Mac Mini (Mid 2010 or newer) Mac Pro (Early 2009 with AirPort Extreme card, or Mid 2010) **The MacBook Pro (17-Inch Late 2008) and the white MacBook (Late 2008) do not support AirDrop.

For help identifying your Mac, choose About This Mac from the Apple menu. You can refer to the Apple Support website to find out if your iPhone, iPad or iPod Touch includes a lightning connector.

So, sadly, there is no known hack to make it work with iOS devices and older Mac's. Would be a great feature though!

There are two versions of AirDrop. The Mac-to-Mac AirDrop that was introduced in Lion works with old Bluetooth modules. The Mac-to-iDevice AirDrop that was introduced in Yosemite only works with newer modules (2012 or later). If you really want to get Mac-to-iDevice AirDrop, you'll need to either upgrade your AirPort card or get a dongle. Continuity Activation Tool is a great app for enabling that feature, and they made a handy chart telling you what hardware you need to put on your computer to make it work with Mac-to-iDevice AirDrop.