Seeking recommendations for SMS / CRM Integration...cannot be app-based integration

Seeking recommendations for SMS / CRM Integration...cannot be app-based integration

Requirements:
  1. Ability to use physical cell phone for both voice and sms. I need to be able to tell my customer "you can call me or text me using this phone number which is my business cell phone".
  2. Unacceptable to use ONLY a stand-alone "sms app".
  3. SMS message to/from given phone numbers attached, as records in a custom module, to the matching phone number in Accounts, 
  4. API-access the SMS crm add-on.
  5. Send SMS from CRM using the cell phone number attached to the CRM user.
Suggestions, please.

Ken