Why not let your cell phone save you money for a change? Several companies have started mobile coupon services that send discount codes for things ranging from ice cream to hotel rooms directly to your phone—when you want them. Market leader Cellfire (cellfire.com) does it without even bothering you with text messages. It downloads a program to your phone that will update the latest deals automatically. You can key in your ZIP code while you’re out shopping to see which coupons are waiting for you. Typical recent offerings included a free shake at Cold Stone Creamery, a free Hollywood Video rental and a double upgrade at Enterprise Rent-A-Car. You can change your ZIP code and see new offers whenever you’re on the move. Other services, including text2store (text2store.com) and PingRewards (ping-mobile.com), send their coupon offers in text messages once you register at their Web sites. You can sign in for specific types of offers, such as restaurant deals, or, at PingRewards, for specific stores where you like to shop. Both allow you to limit the number of interrupting messages you receive; text2store lets you toggle the messaging function on and off so you can stop it if you’re busy (or have run out of spending money for the month). To use the cellular coupons at stores, simply show the cashier the code that pops up on your phone; in many cases you can use the codes for online discounts, too. So far the offerings are a bit familiar: who doesn’t get discounts for Omaha Steaks and 1-800-Flowers? But the buzz is building, and the free ice cream is still pretty sweet.