Buy your daughter a recorder, record him telling her these things. Move up the chain from principal to superintendent until either someone listens or you hire a lawyer to help. You are your daughters advocate!

Not only is your daughter being bullied but she is also being stalked.  You should make a report with your superintendent as well as your local police.  Your daughter should make a log of all inappropriate contact with this teacher as well as any witnesses that are present.  Stalking rarely ends without intervention.  You should also contact your local stalking and abuse center.  They can help guide you through this process.  Below is a National Stalking Website and log to get you started.  They have a wealth of information.  Best wishes to you and your daughter.  If you need further information, contact me through this website and I will be happy to direct you in the right direction.

Advocate for Stalking and Domestic Violence Victims
http://www.ncvc.org/src/main.aspx?dbID=DB_IncidentandBehaviorLog(goodone)759

DEMAND the school to do something about it. If they don't the first couple times, stay persistent. If nothing is done yet, go to the district people. If they do nothing, then pull out the big guns. The law people. I mean, if the teacher watches your daughter OFF campus, that's wierd and inappropriate. But now, if the teacher PUNISHES her for such actions, that's just unacceptable. So, if you must, the law is here for you.

The concerning thing is that he is watching her off school premises.  Does she actually see him?  On what grounds is the teacher giving her detention/ suspension?  I would let the principal know that you are bringing this to the attention of the school board and the local police as he/she is not concerned.  
Demand that action be taken: do not let this teacher have any position of discipline over your daughter.  It is frightening to think that he could have her alone in detention.

For sure make a report with your local police , and go to the school  and get this notice at once,  get a lawyer ASAP .. if you dont put an end
 to this she will withdrew from you and start having behavior problems later on .. you have the right to protect you daughter from bullying.

You are right to be concerned about this behavior.  Is there any way to verify what your daughter has apparently reported?  I expect that the complaint may be taken more seriously if more than one student can describe what is happening based on their own observation.  
If you have only contacted the administrators once, I would try again.  You need to give them as much specific information as possible about what happened, where, and when it happened.  If possible, you and your daughter should do this together.  If the behavior continues, you may need to take the specific information up the chain of administrative command.  
Jeanne H. Brockmyer, Ph. D. education.com clinical psychology expert

First, tell your daughter to not respond to this guy.  Any attention, even negative, is attention that he may like.  Next, go with your daughter's dad or another male figure (uncle, grandfather) and speak to this teacher face to face in a nonviolent way.  Going above him to his boss may just provoke him more.  Letting him know that there are strong male figures in your daughter's life may cause him to back off.  Beyond that, contact your local authorities (sheriff, police).  I would also recommend that you get your daughter in a good martial arts program in order to boost her confidence and equip her in the event (God forbid) she would have have to physically defend herself.

It almost sounds like stalking. Put it all in writing - along with any information from witnesses who hear - tell her not to be alone if possible to keep at least one friend with her. If you put "stalking" concerns in writing and "inappropriate" behavior from a male teacher towards a female student IN WRITING (with copies to the school board if necessary) It may get more attention. If not, you may be able to file a stalking complaint with the police - at least for the off campus incidents.

Talk to the teacher personally and ask him what is his intention of bulling your daughter.Then, always follow up your complaint so that the principal and the dean will know how serious you are and persistent about solving such problem. For sure, make a written complaint.

Go to the school board, if they will not hear you, then seek legal advice.

talk again to the principal and tell her if does not start doing something about it you are going to have to go to the REGIONAL is call here in miami that is like the main office of all the schools and trust me they are going to do somenthing because if you go there they are going to investigate the school and that is not good for them...i hope you understand my english is not very good

This is stalking and if it doesn't stop you need to contact the police and get a restraining order against him. This is unacceptable and should not ber tolerated.

I wish people would stop using "bullying" for everything. Your daughter being constantly watched by someone is called "stalking".  Is he a teacher for one of her classes? Or is he just some teacher at school? I don't see the mystery on what to do mom. If some grown man is following your daughter, you get the police involved!! Also whenever there is a problem like that....contact the school board.