An example of adding ForceTouch to a UIButton using a new UIControlEvent

ForceTouchButton.swift

//
//  ForceTouchButton.swift
//
//  Created by Robert Dougan on 09/10/15.
//  Copyright © 2015 Robert Dougan. All rights reserved.
//

import UIKit

extension UIControlEvents {
    static var ForceTouchDown = UIControlEvents(rawValue: 512)
}

class ForceTouchButton: UIButton {
    
    override func continueTrackingWithTouch(touch: UITouch, withEvent event: UIEvent?) -> Bool {
        if traitCollection.forceTouchCapability == .Available {
            if (touch.force == touch.maximumPossibleForce) {
                self.sendActionsForControlEvents(.ForceTouchDown)
                
                return false
            }
        }
        
        return super.continueTrackingWithTouch(touch, withEvent: event)
    }
    
}

Usage.swift

button.addTarget(self, action: "doAction:", forControlEvents: .ForceTouchDown)