I use Llama to set phone every day and time in various formats. I have not used the function that allows ringtones to sound, when in silent mode - BUT it does have this function. Llama has been perfect for me since it was pointed out to me months ago.
Check it out!
( I have not affiliation with Llama at all - I just love good apps! )
EDIT: Llama uses phone masts to determine your location, so that you can change your ringer, vibrate and ringtones depending on where you are as well as the time of day. Llama provides you with sound profiles so you can quickly switch between quiet, loud, silent and normal sound settings. You can set your family, wife and children to ring even if your phone is set to silent!