If I can just add a couple of points here, it would be a good idea for the client if they have regular weekly catch-up meetings with their developers to gauge progress right from the start of the project - being able to demonstrate what they've done in that particular week in a practical way increases the likelihood of them actually doing and achieving something, and the team gets "buy-in" in on every aspect of the project. If the code isn't ready, let the developers know that's fine - just demonstrate what they've got and point out what's missing. The important thing is to keep it informal and productive i.e. minimal preparation and no "where the hell is that search function you said would be ready?" attitude.
There's no real way to guarantee that the client's developers will be working a 40 hour week - yes, they may be sitting in an office starting at a screen for those 40 hours, but are they being productive? Personally, I find keeping a development log and just recording a start/end time for that particular activity is fairly quick and easy to do and is far less onerous than having to account for every 15 minutes of the working day. If I had a manager standing behind me, asking what I was doing every 5 minutes and telling me which buttons to press, that would be the end of that job for me.
Lastly, isn't it results that count? What happened to "working smarter, not harder"?
I know there's always the potential for people to abuse the system, but that tends to happen when the respect has gone - which is almost always down to poor communication between the two parties or some other kind of grievance that arose at an early stage in the relationship.