Fresh to the Android Market and set to take on Google's Latitude is Glympse, another way of sharing your location with friends, colleagues and family. Glympse attempts to tackle the problem of ongoing privacy present in many location-based apps; that is, you may want to let someone know where you are for a certain period, but not forever.
Generally, location-sharing software works in one of two ways: either a one-off alert, which usually sends out a set of GPS coordinates either by SMS or email, or an ongoing connection as in Google Latitude. While Latitude does allow for privacy settings, such as turning on and off tracking on a per-contact basis, it's something the user needs to remember to switch.
What Glympse offers, instead, is a range of time-controlled tracking invitations. These can run from a single instant, through minutes and several hours. No special software is required by the recipient; instead they merely receive a link which takes them to a web-based map; the sender can also prematurely end or extend the invite. The Glympse app is currently available through the Android Market as a free download, but the company is planning Windows Mobile, iPhone and BlackBerry versions. More details at their FAQ here.