if your loan is so-called Flexi, you can do this.

Or, if your bank allows, you can directly pay to principal, albeit manual instruction to bank officer. Nothing new.

basically, pay as much juice you can squeeze out of yourself    and as fast as you can.

I still don't get how let say your monthly installment is RM1.5k, you pay 2 x RM750 will result in reduction of tenure & interest paid.

For the recent mortgage products, interests are charged on a daily basis, although your installment is being paid only once a month.

For this method to work, it requires a loan account that has flexi facility (not necessarily full-flexi). Even for semi-flexi accounts like the recent OCBC mortgage product (please verify this with your own bank's customer service) the advance payment goes into reducing the outstanding loan. Full flexi is just a fancy word to show that you can freely move money from your savings account to your loan account (for CIMB, they are the same account!) but it comes with a fee of between RM5 to RM20 a month.

Interest is calculated based on the outstanding loan, based on a daily-rest (meaning it is incurred on a daily basis) and by paying bi-weekly, you would save the interest (of the principal portion that you paid in the middle of the month) incurred on your loans by up to 15 days (which is the eventual installment date if you were to pay monthly)

Essentially, this is nothing more than simply paying your loans earlier than you agreed to. It would definitely help, as much how putting a large sum of your bonus into the loan account would reduce the tenure and hence, the interest incurred
You are right in some sense that this is difficult to monitor. But in my opinion, there isn't too much to monitor as all you are doing is paying more on top of your installment, to reduce the outstanding loan thus incurring less and less interests.