diff --git a/src/fd_gridsd.erl b/src/fd_gridsd.erl
index 6b53b00..c969629 100644
--- a/src/fd_gridsd.erl
+++ b/src/fd_gridsd.erl
@@ -21,8 +21,6 @@
 
 -include("$zx_include/zx_logger.hrl").
 
--type mh_str()         :: string().
-
 %% for craig's autism
 -record(sp,
         {recipient :: string(),
@@ -30,13 +28,11 @@
          payload   :: binary()}).
 
 -type search_pattern() :: #sp{}.
+-type sp() :: search_pattern().
 
 -record(s,
-        {current_gen_height         :: pos_integer(),
-         current_gen_hash           :: string(),
-         current_gen_seen_mb_hashes :: [mh_str()],
-         past_gen_seen_mb_hashes    :: [mh_str()],
-         looking_for                :: [search_pattern()]}).
+        {looking_for = [] :: [{sp(), NotifyWhenSeen :: pid()}]}).
+
 -type state() :: #s{}.
 
 
@@ -44,11 +40,15 @@
 %% caller context
 %%-----------------------------------------------------------------------------
 
--spec get_url(Amount, Payload) -> {ok, URL, QR_PNG} | {error, term()}
-    when Amount  :: none | pos_integer(),
-         Payload :: none | binary(),
+-spec get_url(Amount, Payload) -> Result
+    when Amount  :: non_neg_integer(),
+         Payload :: binary(),
+         Result  :: {ok, URL, QR_PNG}
+                  | {error, term()},
          URL     :: string(),
          QR_PNG  :: binary().
+% @doc
+% Very important: amount MUST be an integer >= 0
 
 get_url(Amount, Payload) ->
     gen_server:call(?MODULE, {get_url, Amount, Payload}).
@@ -105,18 +105,66 @@ terminate(_, _) ->
 %%-----------------------------------------------------------------------------
 
 -spec i_get_url(Amount, Payload, From, State) -> Result
-    when Amount  :: none | pos_integer(),
-         Payload :: none | binary(),
-         From    :: {pid(), reference()},
-         State   :: state(),
-         URL     :: string(),
-         QR_PNG  :: binary().
-         Result  :: {ok, URL, QR_PNG, NewState}
-                  | {error, term()}.
+    when Amount   :: non_neg_integer(),
+         Payload  :: binary(),
+         From     :: {pid(), reference()},
+         State    :: state(),
+         Result   :: {ok, URL, QR_PNG, NewState}
+                   | {error, term()},
+         URL      :: string(),
+         QR_PNG   :: binary(),
+         NewState :: state().
 
-i_get_url(Amount, Payload, From, State) ->
+i_get_url(Amount, Payload, {FromPID, _}, State)
+        when is_integer(Amount), Amount >= 0,
+             is_binary(Payload) ->
     NetworkId = fewd:network_id(),
-    Pubkey    = fewd:pubkey(),
-    URL       = gmgrids:encode({spend, NetworkId, Pubkey},
-                               [{amount, Amount}, {payload, Payload}]),
-    
+    Recipient = fewd:akstr(),
+    URL       = gmgrids:encode({spend, NetworkId, Recipient},
+                               [{amount, Amount},
+                                {payload, Payload}]),
+    URLBin    = unicode:characters_to_binary(URL),
+    PNG       = qr:encode_png(URLBin),
+    case i_register(Recipient, Amount, Payload, FromPID, State) of
+        {ok, NewState} -> {ok, URL, PNG, NewState};
+        Error          -> Error
+    end;
+i_get_url(Amount, _, _, _) when (not is_integer(Amount)) ->
+    {error, non_integer_amount};
+i_get_url(Amount, _, _, _) when Amount < 0 ->
+    {error, negative_amount};
+i_get_url(_, _, _, _) ->
+    {error, bad_payload}.
+
+
+i_register(Recipient, Amount, Payload, FromPID, State = #s{looking_for = Patterns}) ->
+    SP = i_sp(Recipient, Amount, Payload),
+    case i_lookup(SP, State) of
+        not_found ->
+            NewPattern  = {SP, FromPID},
+            NewPatterns = [NewPattern | Patterns],
+            NewState    = State#s{looking_for = NewPatterns},
+            {ok, NewState};
+        {found, _} ->
+            {error, already_registered}
+    end.
+
+%% future proofing
+i_sp(Recipient, Amount, Payload) ->
+    {sp, Recipient, Amount, Payload}.
+
+
+-spec i_lookup(SearchPattern, State) -> Result
+    when SearchPattern :: sp(),
+         State         :: state(),
+         Result        :: {found, NotifyPID :: pid()}
+                        | not_found.
+
+% @private look up search pattern and see if we're looking for it
+
+i_lookup(SearchPattern, State) ->
+    #s{looking_for = Patterns} = State,
+    case lists:keyfind(SearchPattern, 1, Patterns) of
+        false       -> not_found;
+        {_, Notify} -> {found, Notify}
+    end.
diff --git a/src/fewd.erl b/src/fewd.erl
index cc74f93..21b86a7 100644
--- a/src/fewd.erl
+++ b/src/fewd.erl
@@ -9,7 +9,7 @@
 -copyright("Peter Harpending <peterharpending@qpq.swiss>").
 -license("BSD-2-Clause-FreeBSD").
 
--export([network_id/0, pubkey/0]).
+-export([network_id/0, pubkey/0, akstr/0]).
 -export([listen/1, ignore/0]).
 -export([start/2, stop/1]).
 
@@ -18,6 +18,7 @@
 
 network_id() -> "groot.testnet".
 pubkey()     -> pad32("fewd demo").
+akstr()      -> gmgrids:akstr(pubkey()).
 
 
 pad32(Bytes) ->