Has anyone used a mobal world phone? I will be in Germany for two weeks and thought this might be a good way to stay in touch with home. I can purchase a phone for $49.00, and will only be charged when I use it.

A question asked and answered a zillon times here. OR, you could go to any german Vodafone (Eplus, T-Mobile, O2) shop, buy a 30€ prepay phone and have incoming free, (outgoing expensive).
And you'll be able to recieve roaming calls on Vodafone in western Europe for 75c per hour.

Yes, I bought one last summer. I use T-Mobile all the time, and that also works in Europe (since it's a GSM service, and my phone has the right freq bands). I bought the Mobal to give my husband to carry because we were spending partial days doing separate things (in separate towns!) and just wanted the convenience.
You definitely do not want to use my plan above if you are going to make frequent or long calls, b/c the per-minute rate is much higher than replacing with a local SIM. We made 10 calls, either to each other or to home, and spent less than $30 airtime.
I didn't want to buy a SIM because the initial price is rather high, then you have to keep it topped up (within 8-9 months?) or the phone number expires. We don't plan on using it that much.
Also, you should be able to unlock the phoneset but I was not successful in doing so.

30€ include a new phone, a SIM card and 10€ of airtime.

Logos...

Vodafone passport 0,75€/hour or do you mean per call?

Right, it's 75c per call up to one hour. Not a bad deal

I used one last year.

I had to know the phone number before I left home since I was chaperoning a group of teens so the "buy in Europe" plan just wasn't effective.

The phone worked fine. I think my total bill was $60 and we did use it numerous times..