Contacts API / Simple CRM

A basic CRM style contacts feature would be useful to keep bulk lists updated all times via API. Tagging users to groups could be used to split contacts into segments (different bulk sms lists, events, customer segments). API could be used to create/update/delete or mark contact as "blacklisted" to avoid ever sending SMS to that number. Support for custom fields would be great for personalization. These contact lists could be used to send out bulk SMS campaigns in few clicks. Added bonus, have message history displayed for each contact (perhaps linking to contact thread).