For reasons not directly related to your specific question, I think you can go ahead and eliminate RDA/Merge Replication as a possible solution. Microsoft does not advertise this (for obvious reasons), but merge replication is not 100% reliable under conditions where the network connection can be dropped in the middle of the replication process (which happens quite frequently with Windows Mobile clients).
The result of this problem is that changes made to client databases are sometimes not fully propagated to the master database, but you get no detectable indication that this has happened. As you can imagine, this is a bad thing, especially if you sold your client on this solution based on the assumption that RDA works as advertised. The only short-term solution we found to this problem was to implement a very clunky double redundancy process to confirm that each record added or modified on the client made it to the server without error. The long-term solution was to never again use RDA for anything.
This problem may have been fixed in recent versions of RDA (our problem occurred with the latest version 2 years ago), but I'll never know (once bitten twice shy).
Update: by the way, I've had many people I've spoken to about this (including Microsoft support techs) deny that this could possibly be true, but it's very easy to verify: add a bunch of data on the client, then start replication, then yank the USB cable out of the device (assuming your client is Windows Mobile connecting through ActiveSync) while in the middle of this.
If I seem slightly miffed, it's partially because this was what the MS tech was finally forced to say (actual quote): "well, just keep replicating - the data will merge eventually".