An app won't really help you for VM since VM generally works by conditionally forwarding your missed/busy/unreachable calls to a VM number. GV voicemail works fine from Canada (I use it) but because you will be forwarding to a US number from a Canadian line you will pay for US long distance and possible for forwarding minutes too (yes, some of our carriers charge extra for forwarding, $3/month for 2500 forwarded minutes or $0.25-$0.35/forwarded minute PPU).
I would suggest you get a local number from freephoneline.ca. Once you have a free number, they offer free VM and you can set it up to email you the VM messages. You just have to forward your Canadian line to it for any conditional calls using the GSM dial codes. You will still have to find out if your carrier charges for conditional call forwarding minutes, but at least you won't pay LD to use it.
Carrier unlocked iPhone 4
Unlimited airtime, Unlimited CAN/US long distance, Unlimited SMS to CAN/US wireless numbers
2500 Call Forwarding minutes to CAN/US numbers
CiD, 6GB
Google Voice for visual voice mail with message transcription, conditional greetings, unlimited messages (vs 35 message cap), remote retrieval from any PC or phone, no auto-purge after 10 days and most importantly no $7-$8 charge.
Bookmarks