diff -Nbaur nethack-3.4.3/include/youprop.h nethack-tinfoil/include/youprop.h
--- nethack-3.4.3/include/youprop.h	2003-12-08 10:39:13.000000000 +1100
+++ nethack-tinfoil/include/youprop.h	2004-12-14 16:19:19.000000000 +1100
@@ -141,9 +141,11 @@
 
 #define HTelepat		u.uprops[TELEPAT].intrinsic
 #define ETelepat		u.uprops[TELEPAT].extrinsic
-#define Blind_telepat		(HTelepat || ETelepat || \
-				 telepathic(youmonst.data))
-#define Unblind_telepat		(ETelepat)
+#define BTelepat		u.uprops[TELEPAT].blocked
+#define Blind_telepat		((HTelepat || ETelepat || \
+				 telepathic(youmonst.data)) \
+                                 && !BTelepat)
+#define Unblind_telepat		(ETelepat & !BTelepat)
 
 #define HWarning		u.uprops[WARNING].intrinsic
 #define EWarning		u.uprops[WARNING].extrinsic
diff -Nbaur nethack-3.4.3/src/eat.c nethack-tinfoil/src/eat.c
--- nethack-3.4.3/src/eat.c	2003-12-08 10:39:13.000000000 +1100
+++ nethack-tinfoil/src/eat.c	2004-12-14 16:20:35.000000000 +1100
@@ -763,7 +763,7 @@
 #ifdef DEBUG
 		debugpline("Trying to give telepathy");
 #endif
-		if(!(HTelepat & FROMOUTSIDE)) {
+		if(!(HTelepat & FROMOUTSIDE) && !BTelepat) {
 			You_feel(Hallucination ?
 			    "in touch with the cosmos." :
 			    "a strange mental acuity.");
diff -Nbaur nethack-3.4.3/src/monmove.c nethack-tinfoil/src/monmove.c
--- nethack-3.4.3/src/monmove.c	2003-12-08 10:39:13.000000000 +1100
+++ nethack-tinfoil/src/monmove.c	2004-12-14 17:33:15.000000000 +1100
@@ -407,7 +407,9 @@
 
 		if (canseemon(mtmp))
 			pline("%s concentrates.", Monnam(mtmp));
-		if (distu(mtmp->mx, mtmp->my) > BOLT_LIM * BOLT_LIM) {
+		/* MRKR: tinfoil hats block psychic energy */
+		if (uarmh && uarmh->otyp == TINFOIL_HAT || 
+		    distu(mtmp->mx, mtmp->my) > BOLT_LIM * BOLT_LIM) {
 			You("sense a faint wave of psychic energy.");
 			goto toofar;
 		}
diff -Nbaur nethack-3.4.3/src/objects.c nethack-tinfoil/src/objects.c
--- nethack-3.4.3/src/objects.c	2003-12-08 10:39:13.000000000 +1100
+++ nethack-tinfoil/src/objects.c	2004-12-14 16:07:06.000000000 +1100
@@ -308,6 +308,8 @@
 		0, 1,  0,	3, 1,  4,   1,10, 0, CLOTH, CLR_BLUE),
 HELM("dented pot", (char *)0,
 		1, 0,  0,	2, 0, 10,   8, 9, 0, IRON, CLR_BLACK),
+HELM("tinfoil hat", (char *)0,
+		1, 1,  0,	0, 0,  0,   1, 10, 0, METAL, HI_METAL),
 /* With shuffled appearances... */
 HELM("helmet", "plumed helmet",
 		0, 0,  0,      10, 1, 30,  10, 9, 0, IRON, HI_METAL),
diff -Nbaur nethack-3.4.3/src/polyself.c nethack-tinfoil/src/polyself.c
--- nethack-3.4.3/src/polyself.c	2003-12-08 10:39:13.000000000 +1100
+++ nethack-tinfoil/src/polyself.c	2004-12-14 17:32:55.000000000 +1100
@@ -1080,6 +1080,10 @@
 	flags.botl = 1;
 
 	You("concentrate.");
+	if (uarmh && uarmh->otyp == TINFOIL_HAT) {
+	    	pline("A wave of psychic energy pours out, but it is blocked by your tinfoil hat.");
+		return 0;
+	}
 	pline("A wave of psychic energy pours out.");
 	for(mtmp=fmon; mtmp; mtmp = nmon) {
 		int u_sen;
diff -Nbaur nethack-3.4.3/src/worn.c nethack-tinfoil/src/worn.c
--- nethack-3.4.3/src/worn.c	2003-12-08 10:39:13.000000000 +1100
+++ nethack-tinfoil/src/worn.c	2004-12-14 16:35:56.000000000 +1100
@@ -37,7 +37,8 @@
 #define w_blocks(o,m) \
 		((o->otyp == MUMMY_WRAPPING && ((m) & W_ARMC)) ? INVIS : \
 		 (o->otyp == CORNUTHAUM && ((m) & W_ARMH) && \
-			!Role_if(PM_WIZARD)) ? CLAIRVOYANT : 0)
+			!Role_if(PM_WIZARD)) ? CLAIRVOYANT : \
+		 (o->otyp == TINFOIL_HAT && ((m) & W_ARMH)) ? TELEPAT : 0)
 		/* note: monsters don't have clairvoyance, so your role
 		   has no significant effect on their use of w_blocks() */