Using the parameter Search Envelope Coordinate System, you can enter reader search envelope parameters in a different coordinate system than the actual data itself; for example you can have data in an Albers coordinate system, but enter a search envelope in Lat/Long.
This function is available in FME 2008+ for any format that has a set of search envelope parameters, which is usually any database plus a number of other formats.
When you run a workspace with this parameter, FME converts the search envelope into the same coordinate system as the source data, then creates a bounding box from that, as what started out as an envelope may no longer be rectangular after a reprojection. For this reason the output area may be slightly larger than specified.