As a couple, We have a joint bank account.
How do we open a joint bitcoin account where we both contribute our income, and money cannot be taken out without consent of both of us?
Thanks.
You don't need any fancy software to do this for you. Just generate a private key (your "account number") offline and with wifi/networking disabled for security, then print the private key onto two pieces of paper, one for him one for you. As long as only you two have the private key, then only you two will have access to the BTC in it. Then you can add the account as a "watch" online and start putting BTC into it, secure in the knowledge that there's no way anyone can steal your BTC online because the private key has never gone online. As soon as you want to take some bitcoin OUT of the 'account', though, then you have to create a wallet and add it as a fully functional online account. I use blockchain.info's [edited in response to reply] wallet system, because it's probably the safest bet for entrusting your key to third party.
P.S: To generate a private key ('account number plus access') offline. Go to an online generator like
http://brainwallet.org/ (make sure it works as a javascript client-side app so it runs offline) and save the web page to your local drive. Then run THAT file when you're offline and unconnected. This will give you a secure key that has never been 'seen' by the internet.