Anyone want to try a script bash or python?
DISCLAIMER : Not a Python Programmer

I can give you a generic algorithm

Let's say you have 4 DB Servers


replicator@10.1.2.% is the Replication User
1 Master (10.1.2.10)
3 Slaves (IP Addresses : 10.1.2.20,10.1.2.30,10.1.2.40)


STEP 01) Run this query

SELECT host FROM information_schema.processlist WHERE user = 'replicator';


Collect host columns into a list.

STEP 02) For each host collected into the list, run

SHOW SLAVE STATUS;


and retrieve the Relay_Master_Log_File column. Collect these in an array.

I wrote about why to pick that field and not Read_Master_Log_File


Aug 02, 2012 : Deleting bin logs in replication environment
May 26, 2012 : Trying to understand SHOW SLAVE STATUS\G
Jan 24, 2012 : Mysql master-master replication auto flush old logs 
Jan 03, 2012 : what are the conditions under which mysql replication might break?


STEP 03) Sort the array of Relay_Master_Log_File names. Select the first entry.

Suppose you collected


mysql-bin.00124
mysql-bin.00123
mysql-bin.00125


After sorting, you would pick mysql-bin.00123

STEP 04) Purge binary logs on the Master using the select binary log

PURGE BINARY LOGS TO 'mysql-bin.00123';


That's it.

Give it a Try !!!