My daughter keeps missing her curfew. What to do about it?

I was about to ask this on Y! Answers of which I am a long time user but I just came across fluther and thought I’d give it a try. My problem is as follows:

We live in Gibraltar which is very safe so our daughter and most other kids walk home from school and since she turned 16 this year we have a rule that she must be home no later than 1 hour after the end of classes (the walk takes about 10 minutes but sometimes she and her friends like to hang out a bit, go into a few shops on the main street and we are fine with that). She also has a curfew of 1am on Friday and Saturday nights which I think it’s quite generous.

Everything went well for a while but since she got her first boyfriend 2 months ago she constantly misses her curfew both on school days and on weekend nights out. We tried talking to her nicely, reducing her allowance proportional to the time being late, grounded her, took her cell phone (not all at the same times obviously) and nothing worked so far.

Now my husband who used to be in the military and who is very upset with her behaviour came up with this physical exercise punishment where if she is late a certain number of minutes past her curfew she has to spend the same number of minutes standing on her tiptoes with her nose on the wall and hands behind back and with one soft tomato or peach under each heel, and if she crushes the peach/tomato the timer is reset and she has to start over. If she is late for more than 60 minutes then she does the tiptoe punishment for 1 hour on one day and the rest of the punishment on the following day (so never more than 60 minutes on one day as it would be physically too difficult).

I have mixed feelings about this but he is very determined to go ahead with it so I was wondering what other people think about it? Also, do you have any other ideas how we could deal with the constant curfew missing given that the traditional methods (grounding, etc.) did not work?