[Samsung Galaxy Nexus] Xdevillived666:
In order for your app to appear in the system settings as an eligible default SMS app, your manifest file must declare some specific capabilities. So you must update your app to do the following things:

In a broadcast receiver, include an intent filter for SMS_DELIVER_ACTION ("android.provider.Telephony.SMS_DELIVER"). The broadcast receiver must also require the BROADCAST_SMS permission.

This allows your app to directly receive incoming SMS messages.

In a broadcast receiver, include an intent filter for WAP_PUSH_DELIVER_ACTION ("android.provider.Telephony.WAP_PUSH_DELIVER") with the MIME type "application/vnd.wap.mms-message". The broadcast receiver must also require the BROADCAST_WAP_PUSH permission.

This allows your app to directly receive incoming MMS messages.

In your activity that delivers new messages, include an intent filter for ACTION_SENDTO ("android.intent.action.SENDTO") with schemas, sms:, smsto:, mms:, and mmsto:.

This allows your app to receive intents from other apps that want to deliver a message.

In a service, include an intent filter for ACTION_RESPONSE_VIA_MESSAGE ("android.intent.action.RESPOND_VIA_MESSAGE") with schemas, sms:, smsto:, mms:, and mmsto:. This service must also require the SEND_RESPOND_VIA_MESSAGE permission.

This allows users to respond to incoming phone calls with an immediate text message using your app.

For example, here's a manifest file with the necessary components and intent filters:

<manifest>

...

<application>

<!-- BroadcastReceiver that listens for incoming SMS messages -->

<receiver android:name=".SmsReceiver"

android:permission="android.permission.BROADCAST_SMS">

<intent-filter>

<action android:name="android.provider.Telephony.SMS_DELIVER" />

</intent-filter>

</receiver>

<!-- BroadcastReceiver that listens for incoming MMS messages -->

<receiver android:name=".MmsReceiver"

android:permission="android.permission.BROADCAST_WAP_PUSH">

<intent-filter>

<action android:name="android.provider.Telephony.WAP_PUSH_DELIVER" />

<data android:mimeType="application/vnd.wap.mms-message" />

</intent-filter>

</receiver>

<!-- Activity that allows the user to send new SMS/MMS messages -->

<activity android:name=".ComposeSmsActivity" >

<intent-filter>

<action android:name="android.intent.action.SEND" />

<action android:name="android.intent.action.SENDTO" />

<category android:name="android.intent.category.DEFAULT" />

<category android:name="android.intent.category.BROWSABLE" />

<data android:scheme="sms" />

<data android:scheme="smsto" />

<data android:scheme="mms" />

<data android:scheme="mmsto" />

</intent-filter>

</activity>

<!-- Service that delivers messages from the phone "quick response" -->

<service android:name=".HeadlessSmsSendService"

android:permission="android.permission.SEND_RESPOND_VIA_MESSAGE"

android:exported="true" >

<intent-filter>

<action android:name="android.intent.action.RESPOND_VIA_MESSAGE" />

<category android:name="android.intent.category.DEFAULT" />

<data android:scheme="sms" />

<data android:scheme="smsto" />

<data android:scheme="mms" />

<data android:scheme="mmsto" />

</intent-filter>

</service>

</application>

</manifest>