I realize that given the way you've constructed this a regex is probably the best way to parse lat/lng out of a WKT string, but I probably would have changed the id_geom and MapWidget to store them in separate fields to make it unnecessary.  Given that it's already working I wouldn't bother rearchitecting it, but I wanted to point it out.

A good quote about regexes I heard once is "Regular expressions are like a particularly spicy hot sauce – to be used in moderation and with restraint only when appropriate".  Perhaps coming from an NLP background they're a more natural tool for you to reach for, but most people find them error prone and difficult to read.  Here's an excellent blog post on the proper use of regexes: http://www.codinghorror.com/blog/2008/06/regular-expressions-now-you-have-two-problems.html .