Async triggers

Is this possible in PG somehow? Basically I need to call web service
whenever new row is inserted in a table - the lookup takes time up to
10-15 seconds. Obviously I cant do this inside trigger proc as that
would delay inserts a lot. I suppose I could do a cron job to do
webservice lookups periodically, but that involves delay and added point
of failure (if cron process stops working for whatever reason). Ideally
async trigger proc would be the solution, but it seems I cant do
asynchronous execution in PG.

Thanks!
Peter