I didn't find anything on the forums about it, a wanted an anchor tool tip to be in a textfield validation with autohide false, and i wanted the posibility to change the img of the anchor element on the tool tip, so i did this little extension and add a new Ext.form.MessageTargets that use this new tooltip for validation.

Code:
/**
  * Ext.ux.AnchorToolTip - Tooltip that supports anchorStyle (CSS Class)
  *
  * @author  Ing. Ulises Acosta
  * @version Ext.ux.AnchorToolTip.js 1.0 2009-07-16 16:15
  *
  * @class Ext.ux.AnchorToolTip
  * @extends Ext.ToolTip
  */
  
Ext.ns('Ext.ux');
Ext.ux.AnchorToolTip = Ext.extend(Ext.ToolTip, {
    /**
     * @cfg {String} anchorImgCls Class of the image of the anchor image (defaults to '')
     * To use it you have to write css rule like this one
     *
     * .custom-anchor-img-class {
     *      background-image : url(custom-anchor-img-sprite.gif);
     * }
     */
    anchorImgCls: '',
	
    // private
    initComponent: function(){
        Ext.ux.AnchorToolTip.superclass.initComponent.call(this);
    },
	
    // private
    onRender : function(ct, position){
        Ext.ToolTip.superclass.onRender.call(this, ct, position);
        this.anchorCls = 'x-tip-anchor-' + this.getAnchorPosition();
        this.anchorEl = this.el.createChild({
            cls: 'x-tip-anchor' + ((this.anchorImgCls == '') ? '' : ' ' + this.anchorImgCls) + ' ' + this.anchorCls
        });
    },
    
    /**
     * Removes this ToolTip from the target element if exists.
     */
    removeTarget : function(){
        if(this.target){
            this.target.un('mouseover', this.onTargetOver, this);
            this.target.un('mouseout', this.onTargetOut, this);
            this.target.un('mousemove', this.onMouseMove, this);
        }
    }
    
});

/**
  *  Extends Ext.form.MessageTargets to have an AnchorToolTip
  *  for validation porpuses with the style x-form-anchor-invalid
  */
  
Ext.apply( Ext.form.MessageTargets, {
    'tooltip' : {
        mark : function(field, msg){
            field.el.addClass(field.invalidClass);
            
            var t = this.invalidtooltip;
            if(!t){
                t = this.invalidtooltip = new Ext.ux.AnchorToolTip({
                    maxWidth       : 600,
                    anchorImgCls   : 'x-tip-anchor-invalid',
                    cls            : 'x-form-invalid-tip',
                    anchor         : 'left',
                    autoHide       : false,
                    anchorToTarget : true
                });
            }
            t.initTarget(field.getEl());
            if(!t.rendered){
                t.show();
                t.hide();
            }
            t.body.update(msg);
            t.doAutoWidth();
            t.show();
        },
        clear : function(field){
            field.el.removeClass(field.invalidClass);
            if(this.invalidtooltip){
                this.invalidtooltip.hide();
                this.invalidtooltip.removeTarget();
            }
        }
    }
});
the css style that i use it in the new messageTargets is this one

Code:
.x-tip-anchor-invalid {
    background-image : url(../img/tip-anchor-invalid-sprite.gif);
}
and the image is this one

tip-anchor-invalid-sprite.gif

the js file is

ext-ux-anchortooltip.zip

all the comments are welcome