Is there a service/application that will allow a "friend" to retrieve my location from my phone without my involvement? I'd like to allow my wife to query my location whenever she's curious. There are no trust issues here, so I don't care about acknowledging/approving her "ping" request, whenever she wants to know she can just request my location details.

Is there an app or service that does this? Most of them (understandably) require that the handset owner allow/permit the request, but I'd like this to happen without my involvement (say I'm busy at the office, driving, or getting groceries).
It sounds like Google Latitude does what you want. Once you opt-in you can then share your location data with your wife, and she should be able to check your location anytime. As far as I know, once you choose share your location data with someone they can retrieve it anytime without having to explicitly request your permission.

Latitude is built into the Google Maps application for Android. You can enable it by going into the application's settings and checking "Enable location sharing", then use the setting right below it ("Manage your friends") to choose who can see your location data.