Hello , im a VoiP systems administrator , reading your project details, it seems you need DTMF signaling to be running on Asterisk system , if it's the case, so it's already included in Asterisk, let me know if im wrong on the DTMF usage that you want, you want for exampl route the customer to a defined extension after Key 1 is pressed in his phone.
thanks to contact me if this is the correct need.
Regards
Kamal zaouli