I really like this idea because it's perfect for a group of people having a few Valentine's Day drinks or just as perfect for a private romantic dinner for two.
You can put the heart shaped ice in a ice bucket or simply have the heart shape ice already in individual glasses. Either way it works because the idea is for the drinker to see the hearts.
You can find heart shape ice cube molds at craft store and in the Valentine section of some supermarkets and retail stores like Wal-Mart. You can even find candy molds that will work for ice cubes as well. If you can't find them in stores just do a search at Amazon.com and you will find them for sure.
Shop Heart Ice Cube Trays
You can either freeze the cubes clear or add a bit of food coloring to the water. Or... add a bit of red fruit juice. You can even fill the molds 1/2 full of water and let it freeze then fill the remainder of the mold up with your choice of a red drink. I love the 1/2 and 1/2 effect myself.