partner-contact/partner_external_maps/partner_view.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
    Copyright (C) 2015 Akretion France (www.akretion.com)
    @author: Alexis de Lattre <alexis.delattre@akretion.com>
    The licence is in the file __openerp__.py
-->

<openerp>
<data>

<!--  Inherit partner view to add 'Map' button -->
<record id="view_partner_form" model="ir.ui.view">
    <field name="name">map.button.res.partner.form</field>
    <field name="model">res.partner</field>
    <field name="inherit_id" ref="base.view_partner_form"/>
    <field name="arch" type="xml">
        <xpath expr="//div[@name='buttons']" position="inside">
            <button class="oe_inline oe_stat_button"
                name="open_map" type="object" string="Map"
                attrs="{'invisible': [('city', '=', False)]}"
                icon="fa-map-marker"/>
            <button class="oe_inline oe_stat_button"
                name="open_route_map" type="object" string="Route Map"
                attrs="{'invisible': [('city', '=', False)]}"
                icon="fa-car"/>
        </xpath>
    </field>
</record>

</data>
</openerp>