Download Ringtones to Smartphone

I’m trying to setup a site where a page will be dedicated to downloading original ringtones for free from smartphones. I can make a ringtone available for download in MP3 format, which works (I can tap, hold, and choose Save Link As from both my laptop and Galaxy Note), but I really want an option for the site to recognize the type of device and ask if you want to download the sound specifically as a ringtone.

Is there some code someone can direct me to that I can use to write into the download link for the site?