Ext RadioGroup - How to Access the value of selected radio button?

function createForm(elem) {
var myForm2 = new Ext.form.FormPanel({
  renderTo:elem,
  width:425,
  frame:true,
  style:"margin: 10px auto 10px auto;",
  items: [{xtype:'fieldset',
			title: 'Contact Info',
			autoHeight:true,
			items :[new Ext.form.RadioGroup({
						fieldLabel: 'Main Phone',
						vertical: false,
						id:"mainPhone",
						items: [
							{boxLabel: 'Home', name: 'id-1', inputValue: 'H', checked:true},
							{boxLabel: 'Work', name: 'id-1', inputValue: 'W'},
							{boxLabel: 'Other', name: 'id-1', inputValue: 'O'}
						]

					}),
				  new Ext.form.TextField({
					id:"frm_CreateCustomerHomePhone",
					fieldLabel:"Home Phone",
					width:275,
					allowBlank:true
				 }),
				 new Ext.form.TextField({
					id:"frm_CreateCustomerWorkPhone",
					fieldLabel:"Work Phone",
					width:275,
					allowBlank:true
				 })
				  new Ext.form.TextField({
					id:"frm_CreateCustomerOtherPhone",
					fieldLabel:"Other Phone",
					width:275,
					allowBlank:true
				 })
	]}]});
}

myForm2.getForm().getValues()['id-1'];

var checkedItem = Ext.getCmp('mainPhone').getValue();

	if (checkedItem == undefined) return '';

	return checkedItem.getGroupValue();
	// The getGroupValue will return the value of the checked option in a group,
	// unfortunately, it only seems to work on the items and not the radiogroup
	// itself

myForm2.getForm().findField('id-1').getGroupValue();

Ext.getCmp("mainPhone").items.get(0).getGroupValue();

var radio = ...;
var value = radio.inputValue;

function get_radio_value()
{
    for( var i=0; i < document.myForm.mainPhone.length; i++ )
    {
       if( document.myForm.mainPhone[ i ].checked )
       {
           return document.myForm.mainPhone[ i ].value;
       }
    }
}