What is the best way to have a Panama phone number that can be answered from abroad?

In order of preference I'm looking for the following solutions:

1) An online number, similar to SkypeIn (unfortunately Skype doesn't offer numbers in Panama) that can be answered on your computer

2) A cellphone with prepaid roaming. Which provider offers the best deal for that?

3) A voice mailbox where messages are delivered by email (similar to eVoice)

Thanks...