diff --git a/core/include/sched.h b/core/include/sched.h
index c30c4ca64056..7b65fe2c92a6 100644
--- a/core/include/sched.h
+++ b/core/include/sched.h
@@ -21,31 +21,84 @@
 #define SCHED_PRIO_LEVELS 16
 #endif
 
+/**
+ * @brief   Initializes thread table, active thread information, and runqueues
+ */
 void sched_init(void);
+
+/**
+ * @brief   Triggers the scheduler to select schedule the next task
+ */
 void sched_run(void);
 
+/**
+ * @brief   Set the status of the specified process
+ *
+ * @param[in]   process     Pointer to the thread control block of the 
+ *                          targeted process
+ * @param[in]   status      The new status of this thread
+ */
 void sched_set_status(tcb_t *process, unsigned int status);
+
+/**
+ * @brief   Switch to thread of higher priority
+ *
+ * @param[in]   current_prio    The priority of the current thread
+ * @param[in]   other_prio      The priority of the target thread
+ * @param[in]   in_isr          1 if currently in interrupt context, 0 otherwise */
 void sched_switch(uint16_t current_prio, uint16_t other_prio, int in_isr);
+
+/**
+ * @brief   Call context switching at task exit
+ */
 void cpu_switch_context_exit(void);
 
+/**
+ *  Request a context switch for the next scheduler run (useful during 
+ *  interrupt handling)
+ */
 extern volatile unsigned int sched_context_switch_request;
 
+/**
+ *  Thread table
+ */
 extern volatile tcb_t *sched_threads[MAXTHREADS];
+
+/**
+ *  Currently active thread
+ */
 extern volatile tcb_t *active_thread;
 
+/**
+ *  Number of running (non-terminated) threads
+ */
 extern volatile int num_tasks;
+
+/**
+ *  Process ID of active thread
+ */
 extern volatile int thread_pid;
 
-//#define SCHEDSTATISTICS
 #if SCHEDSTATISTICS
-
+/**
+ *  Scheduler statistics
+ */
 typedef struct {
-    unsigned int laststart;
-    unsigned int schedules;
-    unsigned int runtime;
+    unsigned int laststart; /*< Time stamp of the last time this thread was
+                                scheduled to run */
+    unsigned int schedules; /*< How often the thread was scheduled to run */
+    unsigned int runtime;   /*< The total runtime of this thread */
 } schedstat;
 
+/**
+ *  Thread statistics table
+ */
 extern schedstat pidlist[MAXTHREADS];
+
+/**
+ *  Register a callback for every scheduler run
+ */
+void sched_register_cb(void (*callback)(uint32_t, uint32_t));
 #endif
 
 /** @} */
diff --git a/core/kernel_init.c b/core/kernel_init.c
index ce378b243130..15f15f2ad1f9 100644
--- a/core/kernel_init.c
+++ b/core/kernel_init.c
@@ -31,8 +31,6 @@
 #include <auto_init.h>
 #endif
 
-volatile tcb_t *sched_threads[MAXTHREADS];
-volatile tcb_t *active_thread;
 volatile int lpm_prevent_sleep = 0;
 
 extern int main(void);
diff --git a/core/sched.c b/core/sched.c
index eb09a629a12d..4ebf5653a90f 100644
--- a/core/sched.c
+++ b/core/sched.c
@@ -37,9 +37,6 @@ volatile int last_pid = -1;
 clist_node_t *runqueues[SCHED_PRIO_LEVELS];
 static uint32_t runqueue_bitcache = 0;
 
-void sched_register_cb(void (*callback)(uint32_t, uint32_t));
-
-
 #if SCHEDSTATISTICS
 static void (*sched_cb) (uint32_t timestamp, uint32_t value) = NULL;
 schedstat pidlist[MAXTHREADS];
@@ -125,7 +122,11 @@ void sched_run()
         thread_pid = (volatile int) my_active_thread->pid;
 #if SCHEDSTATISTICS
         pidlist[my_active_thread->pid].laststart = time;
-        pidlist[my_active_thread->pid].schedules ++;
+        pidlist[my_active_thread->pid].schedules++;
+        if ((sched_cb) && (my_active_thread->pid != last_pid)) {
+            sched_cb(hwtimer_now(), my_active_thread->pid);
+            last_pid = my_active_thread->pid;
+        }
 #endif
 #ifdef MODULE_NSS