Some of the smartphones these days have really nice features to help you find your phone if it gets lost. With the iPhone, for example, you can use Apple’s Find My iPhone to not only get a GPS location of the device, but you can also have it chime to help you realize that it is just sandwiched between your couch cushions.
People who are still using feature phones may not have the same variety of options, but you can still call your phone without needing someone else to do it for you. The site WheresMyCellphone.com lets you put in your phone number and they will call it immediately. Alternatively you can have it called after a delayed amount of time (30 seconds, 1 minute, 2 minutes, or 5 minutes). This service obviously won’t help if you have your phone set to a completely silent mode.
Since you can delay the calls it may also be helpful if you need an excuse to get out of something that is coming up, but unfortunately you can’t specify a delay past 5 minutes so it is only minimally useful in those situations.