The reference discloses a system in which the party called while already on the phone may choose to acknowledge the incoming call - either automatically or by pressing a key.

A cellphone program or service that allows a user to send instant SMS text message reply for both incoming voice calls and SMS messages, stating the reason for the user's unavailability.

The reference details a device that responds to received interrupt events by sending a response based on a GPS location, calendar, and contact book.

PowerSMS is a software program whith many features, one of which allows users to autorespond to missed calls via text message

A feature described in this user manual matches the idea behinds this patent (see page 99 and 119)

The user manual describes a feature that allows for one to press the menu button followed be a "Send Message" button. This allows users to send a default or custom text.

Spb Phone Suite enables Windows Mobile or Android users who installed their software reject calls by pressing one button and opting to send an SMS to the calling party

A manual for setting up a call alert function on a mobile phone, using the service O2 Call Alert, for users in UK or abroad.

Standard network feature provided by Vodafone. Answers calls when phone is engaged, turned off, or out of coverage.

Samsung Galaxy phones have a one-touch "reject with message" feature for unwanted incoming calls

US patent 37921501