You can create your own key by using polymer clay, card stock or use a recycled antique key. Then just simply attach a card or give it to someone with the words "A Key To My Heart"
What you need
Wire Coat Hanger or Heart Floral Frame
2-3 yards or lace
2-3 yards of red ribbon 1/4 inch thick.
1 square of red polymer clay or fimo clay or an antique key
Start this valentines craft by making a wire heart shape out of a coat hanger. Then bind the coat hanger by wrapping the lace around the hanger till all the wire is covered.
Do the same thing with a length of ribbon spacing it out 1 inch as shown in the picture, so the lace shows through.
Make a key out of polymer or fimo clay, it can be as rustic or as intricate as you like. Follow the instructions on your fimo clay for baking the key, then allow it to cool.
Attach the key to the heart with some ribbon, tie a bow and create a long length for hanging the heart.
Alternatively you could create this project without the heart and just attach the key to a handmade card.