diff --git a/alt/big.py b/alt/big.py
index e68fddb..d27a455 100755
--- a/alt/big.py
+++ b/alt/big.py
@@ -321,7 +321,7 @@ def assemble(f, min_static=16, max_static=1023, builtins=BUILTIN_SYMBOLS):
 CYCLES_PER_CALL = 100  # Number of cycles to run in the tight loop (when not tracing)
 
 
-def run(program, chip=BigComputer, simulator="codegen", name="Flat!", font="monaco-9", halt_addr=None, trace=None, verbose_tty=True):
+def run(program, chip=BigComputer, simulator="codegen", name="Flat!", font="monaco-9", halt_addr=None, trace=None, verbose_tty=True, meters=None):
     """Run with keyboard and text-mode graphics."""
 
     # TODO: font
@@ -407,7 +407,8 @@ def run_trace():
             cps = (cycles - last_cycle_count)/(now - last_cycle_time)
             msgs.append(f"{cps/1000:0,.1f}k/s")
             msgs.append(f"@{computer.pc}")
-            # TODO: let the caller add meters (e.g. Ribbit heap consumption)
+            if meters:
+                msgs.extend(meters(computer, cycles))
             pygame.display.set_caption(f"{name}: {'; '.join(msgs)}")
 
             last_cycle_time = now
diff --git a/alt/scheme/rvm.py b/alt/scheme/rvm.py
index 9f2a55b..16ea55a 100755
--- a/alt/scheme/rvm.py
+++ b/alt/scheme/rvm.py
@@ -154,12 +154,23 @@ def trace(computer, cycles):
         elif trace_level >= TRACE_ALL:
             print(f"{cycles:3,d}: {computer.pc}")
 
+    def meters(computer, cycles):
+        inspector = Inspector(computer, symbols, stack_loc)
+        next_rib = unsigned(inspector.peek(next_rib_loc))
+        current_ribs = (next_rib - big.HEAP_BASE)//3
+        max_ribs = (big.HEAP_TOP - big.HEAP_BASE)//3
+        return {
+            f"mem: {100*current_ribs/max_ribs:0.1f}%"
+        }
+
+
     big.run(program=instrs,
             simulator=simulator,
             name="Scheme",
             halt_addr=halt_loop_addr,
             trace=trace if trace_level > TRACE_NONE else None,
-            verbose_tty=verbose_tty)
+            verbose_tty=verbose_tty,
+            meters=meters)
 
 
 def compile(src):