The free Starbucks Cup Magic for iPhone app gained attention for its entertaining Augmented Reality interaction with Red Cup beverages at Starbucks. You can see what I found for the latte I bought in the video embeddded below. However, if you are in the U.S., there is one more feature you might find useful: eGifting.
There are a variety of card designs to choose from. A message of up to 160 characters can be added to the card. Starbucks eGift Cards can be given in any amount you choose. However, the app provides preset options amounts too. eGifts are delivered via email and can be scheduled.
If you do not have an iPhone, you can use this web page to send Starbucks eGift cards.