How to remove unwanted spaces at the right of CheckBox?

by default, the Checkbox has minWidth and minHeight value

you can set its value to 0

<CheckBox
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:minWidth="0dp"
    android:minHeight="0dp" />

The result will be like that without any extra spaces

You can wrap CheckBox in LinearLayout and then use android:gravity="center" on that layout.

 <LinearLayout
    android:layout_height="wrap_content"
    android:layout_width="0dip" 
    android:layout_weight=".20"              
    android:background="#ff0000" 
    android:gravity="center">

    <CheckBox android:id="@+id/bus_route_list_item_reminder" 
        android:layout_height="wrap_content" 
        android:layout_width="wrap_content"                     
    />

</LinearLayout>

As another alternative, you can use RelativeLayout. This would greatly simplify you layout and you will be able to get rid of layout_weight.