Platform recommendations - Geofenced SMS text messages for a restaurant business?

I'm working with a restaurant that wants to send text messages to customers that are within a certain radius of the restaurant (or within a certain zip code would also be fine).

These text messages would only be sent to customers that had previously opted-in to receiving text messages.

The idea is to send text messages to customers at 10:30 AM to inform them of lunch specials that day.

Anyone have any recommendations for SMS platforms that can send based on the users current location?