I lost my remote for my Apple TV3 is there any other way to control it with my Mac or iPad?
you can control your apple tv by using iphone by installing a an application called remote which is available to download from apple for free
You can certainly control your Apple TV with your iPhone by downloading the 'Remote' app on the iOS App Store (http://www.apple.com/apps/remote/)
You can control it easilly through your iDevices. do a little search like "using iphone to control apple tv", it won't do you no harm.
If you lose the Apple Remote that you paired with Apple TV, a replacement remote will not work until you unpair Apple TV from the lost remote
How to connect Apple TV to WiFi without Apple TV Remote
If you've already turned on Home Sharing, you can control it with an iOS device (iPhone, iPad, or iPad Mini). If you haven't turned on Home Sharing, the only other option I know of would be to get a really good universal remote, such as the Logitech Harmony. Your average drugstore universal remotes generally won't work for something like this.
Logitech Harmony that is expensive but as you said universal:)
you can use iphone /ipad app to use it as universal remote follow this link for more http://www.soundandvisionmag.com/article/review-best-iphone-universal-remote-apps