(MONEY Magazine) – Mortgage borrowers who missed getting in under the 8% wire may get a second chance. At least two national lenders are offering fixed-rate mortgages with a rate that automatically drops whenever interest rates fall--and doesn't go up when interest rates rise.

At San Diego-based City Line Mortgage (see the box below for contact information), you'll be notified whenever the market average falls half a percentage point below your current rate. Once you submit proof that your income hasn't dropped (a recent pay stub will do), you'll get the lower rate within days. All you'll pay is a few hundred dollars to cover escrow fees--far less than you'd likely pay to refinance. In late October, City Line's 8% rate for a 30-year fixed mortgage was right in line with other lenders'.

With Fairfax, Va.-based lender Service Savers, you'll pay a slightly higher interest rate up front (3/8% to 1/2% above the average) but no closing costs on the original mortgage. You'll be automatically notified of every quarter-point rate drop but can't take advantage of new lows more than once every 120 days.

What's the catch? Surprisingly, none. Since mortgage companies make a fixed fee for servicing a loan, no matter the rate, retaining creditworthy customers when the next refinancing wave begins is key--and worth absorbing the cost of multiple refinancings.

--JOAN CAPLIN