I have tried many voice recording type applications and the best I have found only allows me to do a recording upto a maximum file size of 2.1GB. I can do many of these 2.1GB recordings as I have a fairly large SD card.
On one of the applications I have tried, the developer has specifically said that his/her app has no recording length limit
So my question, does Android have a built in 2.1GB limit per file?
Short Answer: Yes
More Detailed Answer:
The file size limit is not something specific to Android, it is a limit of the File System.
It may "technically" be a bug in Android though, as FAT32, which is what the file system is for the sdcard, should have a file size limit of 4GB ((2^32)-1 = 4,294,967,295B) but it looks like the filesystem on Android is android is actually using a limit of ((2^31) - 1 = 2,147,483,647B). Which means they could be using signed integers, instead of unsigned integers for the addressing on the filesystem.