The only Bernese Mountain Dog I have ever met is a Theray Dog for Kids. Very sweet natured and always at her owner side even off leash.

http://www.ctac.cat/portal/index.php?sect=1&lang=en

http://www.ctacgirona.com/CTAC_GIRONA/Benvinguts.html
( In case you wonder what lenguage it is, is Catalan)

I would go for a German Shepherd Dog. Lived alone in the country for a few months with the family GSD dog and always felt secure. I can't say enough good things about him. Any stranger would dread step out the car till we said him they were ok. We could tell from his bark who was approaching, he could distinguish the sound of the family's card from th others, good with kids and others animals of the house. I could go on and on...Strong,highly intelligent and loyal to his humans beyond mesure. He was the perfect dod.