Coin is a new emerging company developing a card aggregator that offers to put many credit and membership cards (up to 8 at a time) into a single device that can be used as a swipe device (like a credit card). They are taking pre-orders right now for half ($55) of their expected regular price, to be shipped starting in Summer of 2014. The device works on low power Bluetooth that is expected to last about 2 years, after which a new card will have to be purchased. It works with a single mobile device (iOS or Android) as a partnership.
They have safety precautions in case the card is separated from the mobile device (gives you a notification) or a server takes the card away from the table (the card cannot be changed). The selected card can be toggled while Coin is near the mobile device to let you pick the desired card. Coin will only let you scan in cards that have your name on them.
The mobile device, along with an included dongle (like Square's dongle through the audio port), is used for scanning the credit or membership card (virtually unlimited number). A photo of the card must also be taken. Once in the mobile device has the information, the card information can be downloaded to Coin and it is ready to be swiped.
Pros: your wallet becomes much thinner, the strip on the back is much more resilient than a credit card, works with swipe m
Cons: vendors may look at you strange for a while, the device has to be replaced eventually, a mobile device should be able to be used in this day an age without a card swipe, it doesn't work internationally, still should carry a backup card, it is only water resistent