Index: uspace/drv/time/cmos-rtc/cmos-regs.h
===================================================================
--- uspace/drv/time/cmos-rtc/cmos-regs.h	(revision f87ea202dcfd3bf80f585175f193d1517fdce2fd)
+++ uspace/drv/time/cmos-rtc/cmos-regs.h	(revision d8a4e79428fd53331b868a1ad778c5794ab317aa)
@@ -40,4 +40,7 @@
 #define RTC_MASK_BCD    0x04
 
+#define RTC_STATUS_D    0x0D
+#define RTC_BATTERY_OK  0x80
+
 #define RTC_UPDATE      0x0A
 #define RTC_MASK_UPDATE 0x08
Index: uspace/drv/time/cmos-rtc/cmos-rtc.c
===================================================================
--- uspace/drv/time/cmos-rtc/cmos-rtc.c	(revision f87ea202dcfd3bf80f585175f193d1517fdce2fd)
+++ uspace/drv/time/cmos-rtc/cmos-rtc.c	(revision d8a4e79428fd53331b868a1ad778c5794ab317aa)
@@ -46,4 +46,5 @@
 #include <device/hw_res.h>
 #include <devman.h>
+#include <ipc/clock_ctl.h>
 
 #include "cmos-regs.h"
@@ -82,4 +83,6 @@
 static int  rtc_register_read(rtc_t *rtc, int reg);
 static int  bcd2dec(int bcd);
+static void rtc_default_handler(ddf_fun_t *fun,
+    ipc_callid_t callid, ipc_call_t *call);
 
 
@@ -114,5 +117,5 @@
 
 	rtc_dev_ops.interfaces[CLOCK_DEV_IFACE] = &rtc_clock_dev_ops;
-	rtc_dev_ops.default_handler = NULL; /* XXX */
+	rtc_dev_ops.default_handler = &rtc_default_handler;
 }
 
@@ -387,4 +390,25 @@
 }
 
+/** Default handler for client requests not handled
+ *  by the standard interface
+ */
+static void
+rtc_default_handler(ddf_fun_t *fun, ipc_callid_t callid, ipc_call_t *call)
+{
+	sysarg_t method = IPC_GET_IMETHOD(*call);
+	rtc_t *rtc = RTC_FROM_FNODE(fun);
+	bool batt_ok;
+
+	switch (method) {
+	case CLOCK_GET_BATTERY_STATUS:
+		batt_ok = !(rtc_register_read(rtc, RTC_STATUS_D) &
+		    RTC_BATTERY_OK);
+		async_answer_1(callid, EOK, batt_ok);
+		break;
+	default:
+		async_answer_0(callid, ENOTSUP);
+	}
+}
+
 /** Open the device
  *
Index: uspace/lib/c/include/ipc/clock_ctl.h
===================================================================
--- uspace/lib/c/include/ipc/clock_ctl.h	(revision d8a4e79428fd53331b868a1ad778c5794ab317aa)
+++ uspace/lib/c/include/ipc/clock_ctl.h	(revision d8a4e79428fd53331b868a1ad778c5794ab317aa)
@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2012 Maurizio Lombardi
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ * - The name of the author may not be used to endorse or promote products
+ *   derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef LIBC_IPC_CLOCK_CTL_H_
+#define LIBC_IPC_CLOCK_CTL_H_
+
+#include <ipc/dev_iface.h>
+
+typedef enum {
+	CLOCK_GET_BATTERY_STATUS = DEV_FIRST_CUSTOM_METHOD,
+} clock_ctl_t;
+
+#endif
+